Clemson, Alabama and Notre Dame (and UCF) each went undefeated during the 2018 college football regular season, but which of this year's top contenders for the national championship has the best odds of piecing together a 12-0 campaign?

First, please note that we're only talking about regular season here. Factoring in conference championships and the College Football Playoff would drastically change these odds, but our goal is to affix a number to each team's chance of entering December without a loss.

It should go without saying—but let's state it anyway—that the two biggest factors in this exercise are the overall strength of the team and the difficulty of its schedule.

Alabama and Clemson are co-favorites to win the national championship, but one has better odds of going 12-0 because of its schedule. Similarly, Georgia and LSU might be better than both Michigan and Oklahoma, but the SEC teams have much worse odds of running the table because of the challenges coming their way.

Teams are listed in ascending order of our odds of going undefeated. Also listed for context are the current odds to win the national championship, according to Caesars, where these are the 10 teams with the best odds.

Texas Longhorns

Title Odds: +2000 (20-1)

Undefeated Odds: 500-1

Biggest Hurdles: vs. LSU (Sept. 7), vs. Oklahoma in Dallas (Oct. 12), at Iowa State (Nov. 16)

Among these 10 teams, ESPN's Football Power Index is least optimistic about Texas, and it's not even close. In that predictive metric, the Longhorns are rated as the 24th-best team. They are projected for 4.6 losses and only have a better than 72 percent chance of winning four of their 12 games.

The only other team on this list anywhere close to those numbers is Nebraska.

Part of the reasoning is that while the other eight teams have been consistently relevant, recent history has not been kind to Texas. The Longhorns finished strong last year with a Sugar Bowl win over Georgia, but it was their first season with eight or more victories since 2013.

While we don't know what minutiae goes into the FPI formula, it's safe to assume the preseason model factors in the past three or five years to some extent. That's no bueno for Texas.

But this is also one of the tougher schedules outside of the SEC.

In addition to the three biggest hurdles listed above, the Longhorns have road games against TCU and Baylor that FPI is projecting them to lose by a slim margin. The home games against Kansas, Kansas State and Texas Tech should be easy victories, but Texas has to play four away games against opponents who should finish top-six in the Big 12 standings. Maybe quarterback Sam Ehlinger and Co. win two or three of those, but all four is unlikely at best.

Throw in the Week 2 home game against LSU, and the odds of winning 12 straight are beyond slim to none.

Nebraska Cornhuskers

Title Odds: +2500 (25-1)

Undefeated Odds: 400-1

Biggest Hurdles: at Colorado (Sept. 7), vs. Ohio State (Sept. 28), at Minnesota (Oct. 12), at Purdue (Nov. 2), vs. Iowa (Nov. 29)

Let Nebraska serve as a reminder that betting odds and actual odds are often quite different.

The Cornhuskers won four of their final six games last season, and they have a head coach (Scott Frost) who went 13-0 in 2017 with UCF. Because of that, this potential breakout team has been listed as a sexy sleeper by so many college football fans and analysts that its championship odds are ridiculously inflated.

Will Nebraska be better than last year? Almost definitely. Although this team lost a 1,000-yard rusher (Devine Ozigbo) and a 1,000-yard receiver (Stanley Morgan Jr.), Adrian Martinez is an incredible talent at quarterback who should just about single-handedly get the Huskers to a bowl game.

Could they win 11 games for the first time since 2001? Maybe, if we factor in the possibility of a Big Ten Championship Game and the probability of a bowl. Even if Nebraska's defense struggles—it allowed more than 30 points in eight of 12 games last year—the schedule isn't that daunting.

The Cornhuskers don't face Michigan, Michigan State or Penn State, and they get Ohio State, Iowa, Wisconsin and Northwestern at home. Let's put it this way: Give this slate to a top-10 team, and anything short of an undefeated season would be a disappointment.

Is there a chance they'll go 12-0? Not much of one. Although there isn't a guaranteed loss, the only certain wins are the early home games against South Alabama and Northern Illinois. It's just one coin-flip game after another for three months, which eventually will result in at least one loss.

Notre Dame Fighting Irish

Title Odds: +3000 (30-1)

Undefeated Odds: 100-1

Biggest Hurdles: at Georgia (Sept. 21), at Michigan (Oct. 26)

Notre Dame was one of four teams to enter bowl season with an undefeated record last year, but a step backward seems almost inevitable. The Fighting Irish lost their top rusher (Dexter Williams), two of their top receivers (Miles Boykin and Alize Mack) and four of their best defenders (Julian Love, Jerry Tillery, Te'Von Coney and Drue Tranquill).

But even if you believe that Notre Dame can withstand all that attrition and remain as competent as last season, this schedule has two of the biggest land mines possible in the form of road games against CFP contenders Georgia and Michigan.

Even Alabama and Clemson would have something like 10-1 odds of running the table if those two games were on their calendars.

The rest of Notre Dame's schedule isn't too bad. There are nine games the Fighting Irish ought to win and a regular-season finale at Stanford that's probably close to a coin flip. One need not squint too hard to find 10 wins and a spot in a New Year's Six bowl game. An undefeated season would require a minor miracle, though.

LSU Tigers

Title Odds: +2000 (20-1)

Undefeated Odds: 45-1

Biggest Hurdles: at Texas (Sept. 7), vs. Florida (Oct. 12), vs. Auburn (Oct. 26), at Alabama (Nov. 9)

Per usual, it's a long row to hoe for LSU.

Just by being in the SEC East, the Tigers have to contend with three of the 15 (or so) best teams in the country. At least two of the three (Auburn and Texas A&M) are at home this year, but that road game against Alabama is going to be a significant problem.

The Crimson Tide have won eight straight in this rivalry, and each of the last three in Tuscaloosa was decided by at least a two-touchdown margin. And not only was LSU shut out 29-0 in the bayou last year, but also, the last time the Tigers scored more than 17 points against Alabama was in 2010. And if you think 17 points is going to be enough to win a game against this Tua Tagovailoa-led offense, you're in for a rude awakening.

On top of that colossal road block, LSU will face Florida for the 49th consecutive year and will play a road game against Texas in Week 2. Both of those teams reside in the top 10 of the preseason coaches poll, meaning it's nothing close to a guarantee that Tigers will start 6-0, let alone flirt with 12-0.

Even if LSU gets past Texas, the mid-October three-game gauntlet of vs. Florida, at Mississippi State, vs. Auburn will likely produce a loss before the trip to Alabama brings another.

From a talent-based perspective, LSU should be one of the five best teams in the country. Against this schedule, though, the record might not reflect that.

Ohio State Buckeyes

Title Odds: +1000 (10-1)

Undefeated Odds: 40-1

Biggest Hurdles: at Nebraska (Sept. 28), vs. Michigan State (Oct. 5), at Northwestern (Oct. 18), vs. Penn State (Nov. 23), at Michigan (Nov. 30)

Could Michigan and Ohio State both be 11-0 for the regular-season finale?

It wouldn't be the first time. It happened in 2006 and turned into one of the biggest and most entertaining regular-season games ever played. And now that there are four spots in the College Football Playoff instead of just the BCS Championship Game, it's feasible that both teams would still get a chance to play for a title, regardless of the outcome.

Ohio State's nonconference schedule isn't going to keep that scenario from coming to fruition. The Buckeyes play three home games against Florida Atlantic, Cincinnati and Miami (Ohio), which is about as easy as it gets for a CFP contender. Cincinnati should put up a decent fight, but no one is realistically expecting the Bearcats to win that contest.

Conference play is a different story, though. In addition to the annual battles with Michigan, Michigan State and Penn State, the Buckeyes open Big Ten play with a tricky mid-September road game against Indiana and have tough cross-divisional games against Nebraska, Northwestern and Wisconsin.

While Ohio State should be the favorite in each of its first 11 contests, the only gimmes in conference play are the road game against Rutgers and maybe the home game against Maryland—although the Terrapins gave OSU one heck of a run for its money last November.

Based on ESPN's FPI projections, Ohio State only has a 4 percent chance of starting 11-0. Factor in the 23.4 percent win probability in the final game at Michigan, and the Buckeyes' odds of going 12-0 are allegedly around 100-1.

We're a little more optimistic than that, but combining this schedule with last year's atrocious defense, a new head coach (Ryan Day) and a new starting quarterback—expected to be Justin Fields, who has only been with the program since January—sounds like a recipe for at least one loss.

Georgia Bulldogs

Title Odds: +700 (7-1)

Undefeated Odds: 12-1

Biggest Hurdles: vs. Notre Dame (Sept. 21), vs. Florida in Jacksonville (Nov. 2), at Auburn (Nov. 16), vs. Texas A&M (Nov. 23)

Most regard Georgia as the clear-cut third-best team behind Alabama and Clemson. The Bulldogs won't face either of those squads during the regular season, though, nor will they need to deal with Oklahoma, LSU, Ohio State or Michigan.

So why are we giving them such pedestrian odds of going undefeated?

While Jake Fromm, D'Andre Swift and Co. won't draw any of the top challengers for the national championship, their schedule is loaded with opponents in that next tier of teams capable of doing damage. According to ESPN's FPI ratings, Georgia plays seven games (three away from home) against top-20 foes.

Whether Tennessee, South Carolina and Missouri belong in that top 20 is another story, but even if we ignore those three teams and just focus on the four biggest hurdles listed above—each of which is ranked in the Nos. 8-16 range of the preseason coaches poll—this is undeniably one of the toughest schedules among these nine contenders.

Throw in the fact that three of those four games will come in a four-week span near the end of the regular season, and the path to 12-0 looks even tougher. It's not impossible, but it's far from probable.

If Georgia does go undefeated, though, and beats Alabama in the SEC championship before knocking off both the Crimson Tide and Clemson in the College Football Playoff, you can go ahead and cement it as the greatest season in the history of college football.

Michigan Wolverines

Title Odds: +1200 (12-1)

Undefeated Odds: 9-1

Biggest Hurdles: at Penn State (Oct. 19), vs. Notre Dame (Oct. 26), vs. Ohio State (Nov. 30)

Is this the year that head coach Jim Harbaugh finally gets a win against Ohio State?

If so, the Wolverines might go undefeated, as they are one of just five teams—along with Clemson, Alabama, Georgia and Oklahoma—projected by ESPN's FPI as the favorite in all 12 games.

One of the biggest unknowns facing Michigan is the addition of offensive coordinator Josh Gattis. Will the former Alabama co-offensive coordinator who spent eight seasons as a wide receivers coach be able to put Shea Patterson to better use in more of an aerial-heavy offense, or will Harbaugh keep Michigan on the run-first approach to which he is so accustomed?

The good news is the Wolverines have some time to work out the kinks. Three of their first four games are should-win affairs at home against Middle Tennessee, Army and Rutgers. And even though the Sept. 21 road game against Wisconsin won't be a walk in the park, they get one of their bye weeks before it to better prepare.

Going back-to-back against Penn State and Notre Dame could be a challenge, but neither of those teams is likely to be as good as it was last year. We've previously discussed the Fighting Irish's litany of roster changes, and the Nittany Lions are in a similar predicament. They should be stout on defense, but that should be a low-scoring game that Michigan can win.

Even if the Wolverines get to 11-0, though, that leaves the matchup against Ohio State, which they have lost seven consecutive times, as well as 14 of the last 15. Michigan should be the better team this year and has the luxury of hosting the Buckeyes in the Big House instead of traveling to the Horseshoe, but it won't be easy.

Oklahoma Sooners

Title Odds: +800 (8-1)

Undefeated Odds: 7-1

Biggest Hurdles: at UCLA (Sept. 14), vs. Texas in Dallas (Oct. 12), vs. Iowa State (Nov. 9), at Baylor (Nov. 16), at Oklahoma State (Nov. 30)

Behind the strength of an insatiable offense—and in spite of a defense that has consistently resided somewhere between "not great" and "downright awful"—Oklahoma has won at least 11 games in each of the past four seasons. Even with the switch from Kyler Murray to (presumably) Jalen Hurts at quarterback, this will once again be one of the nation's elite offenses.

As with Ohio State, the nonconference schedule shouldn't be a problem. The Sooners open with home games against Houston and South Dakota for what should be a pair of blowout victories. And unless UCLA is drastically improved three weeks into Chip Kelly's second season at the helm, that road game against the Bruins won't be much more competitive than last year's 49-21 beatdown. That said, it's still on the road against a Power Five opponent, so they best bring their A game.

If a loss is in the cards for coach Lincoln Riley's men, it'll most likely come in conference play. However, there haven't been many of those lately. The Sooners are 35-3 in Big 12 games since the start of 2015, and each of the three losses was a stunner decided by a one-possession margin. They are every bit the class of their conference that Alabama and Clemson are in the SEC and ACC, respectively.

Texas was responsible for two of those three conference losses, though, and has made quite the push back to national relevance. Quarterback Sam Ehlinger ran amok against Oklahoma's defense in last year's upset and will be looking to throw his 10-gallon hat into this year's Heisman conversation with a similar performance. That Red River rivalry game is the clear-cut largest hurdle standing in Oklahoma's path to perfection.

But the Sooners should get the victory. In fact, ESPN's FPI projection gives them at least a 73 percent chance of winning each Big 12 game. Oklahoma hasn't run the table during the regular season since 2004, but there's a reasonable possibility it'll get the job done this year.

Alabama Crimson Tide

Title Odds: +230 (23-10)

Undefeated Odds: 3-2

Biggest Hurdles: at Texas A&M (Oct. 12), vs. LSU (Nov. 9), at Mississippi State (Nov. 16), at Auburn (Nov. 30)

Alabama has gone 35-1 during the regular season over the past three years and has not suffered multiple losses in a regular slate since 2010. There are always a bunch of potential land mines in SEC play, but head coach Nick Saban and the Crimson Tide have done a masterful job of avoiding most of them for nearly a decade.

And with so many returning studs on offense and a more-than-reasonable expectation of improvement on defense, this might be Alabama's most dominant season of the 2010s.

Per usual, Alabama's nonconference schedule is a joke. The Crimson Tide play a neutral-site game against a Duke squad that might finish in last place in the ACC, and then they have home games against New Mexico State, Southern Mississippi and Western Carolina. The combined margin of victory in those four "contests" may exceed last year's total of 162.

Their SEC schedule is arguably easier than normal too. They don't need to play the second-best (Georgia) or fourth-best (Florida) teams in the conference, and they get the third-best (LSU) at home after a bye week. They will also get a bye before facing the SEC's fifth-best team (Texas A&M). And with all due respect to Western Carolina, Alabama is essentially getting the week off prior to facing the SEC's sixth-best team (Auburn).

Aside from drawing LSU and Mississippi State back-to-back in November, there's nothing resembling a trap game or a multiweek gauntlet.

There's always a chance Alabama could lose that Iron Bowl at Auburn. After all, that's the only regular-season loss the Crimson Tide have suffered since Week 3 in 2015. But it's looking good for them to go 12-0 for the third time in four years.

Clemson Tigers

Title Odds: +230 (2.3-1)

Undefeated Odds: 3-4

Biggest Hurdles: vs. Texas A&M (Sept. 7), at Syracuse (Sept. 14), at South Carolina (Nov. 30)

It would be a bit surprising if Alabama suffers a loss prior to the SEC championship, but it's at least conceivable.

If Clemson drops a game prior to the College Football Playoff, though, it would be a flabbergasting turn of events.

The Tigers do have moderately difficult back-to-back games in Weeks 2 and 3, but will the offenses for either Texas A&M or Syracuse be up to the task that early in the season? The Aggies are replacing nearly 3,000 yards of total offense with running back Trayveon Williams and tight end Jace Sternberger now in the NFL, and the Orange have the daunting task of replacing both a four-year, dual-threat starting quarterback in Eric Dungey and top receiver Jamal Custis.

If those games were taking place in November after the offenses had a chance to jell, the odds of an upset would be much higher. But with those new-look attacks getting a first true test by trying to keep pace with the well-established core of Trevor Lawrence, Travis Etienne, Tee Higgins and Justyn Ross, things could get ugly.

Beyond that, the Tigers' ACC schedule should be a walk in the park. Their other road games are against teams in rebuilding mode (Louisville, North Carolina and NC State) and they don't need to face any of the teams expected to vie for the Coastal Division crown (Miami, Virginia and Virginia Tech). The home game against Florida State is the toughest of the bunch, and Clemson should win that by multiple touchdowns.

The biggest challenge is the season finale at South Carolina, though that hasn't been much of a struggle lately. Clemson has won five straight against its in-state rival, four of them by at least an 18-point margin. Unless the Gamecocks can snap that skid, Clemson should go 12-0.

Kerry Miller covers college football and men's college basketball for Bleacher Report. You can follow him on Twitter, @kerrancejames. Recruit ratings courtesy of 247Sports' composite rankings.