There have been weeks of buildup for tonight’s highly anticipated college football national championship game between Florida and Ohio State. But judging by the disappointing ratings thus far for the Bowl Championship Series, new BCS carrier Fox just might sink to record lows for its bowl finale.

Through the first three BCS games, Fox’s household ratings are down 28 percent compared with last year’s bowls on ABC. The Fiesta, Orange and Sugar bowls have averaged a cumulative 24.7 household rating, down from last year’s 34.2.

Among adults 18-49, ratings are down 22 percent, from a 17.8 to a 13.9.

No game so far has topped 15 million viewers. That may mean Fox will fall below 2002’s BCS title game record low of 21.6 million viewers for Miami vs. Nebraska.

Last year was an exceptionally strong one for the early BCS games, what with a triple overtime game between legendary coaches Joe Paterno at Penn State and Bobby Bowden at Florida State and a matchup of two of college’s most popular teams, Notre Dame and Ohio State.

Even so, the year-to-year dip has been quite sharp. Fox finished behind NBC in adults 18-49 on Orange Bowl night, a year after ABC won every night of its BCS coverage handily. And all three bowls posted some of their lower ratings of the past decade.

There are several factors hurting the numbers, all of which could affect tonight’s finale, which kicks off at 8:15 p.m.

The first is competition. Fox not only faced the premieres of broadcast shows like the CW’s “Beauty and the Geek,” which set series highs among some key demographics, and ABC’s “The Knights of Prosperity,” it was likely hurt by cable as well.

FX’s “Dirt” debuted opposite Tuesday’s Orange Bowl, drawing a solid 3.7 million total viewers and 2.4 million 18-49s. The Orange Bowl, by contrast, drew 10.7 million viewers. Monday’s Fiesta Bowl aired opposite strong premieres for E!’s “High Maintenance 90210,” ABC Family’s “Wildfire” and MTV’s “Next.”

And tonight the competition is even tougher. Last year the broadcast networks mostly aired repeats against the BCS title game. Tonight, ABC and CBS have entirely original lineups, while NBC airs a new “Deal or No Deal” to lead off the night.

On cable, ABC Family and VH1 have three shows premiering between them, and Lifetime has the heavily promoted movie “To Be Fat Like Me” and the new reality show “Gay, Straight or Taken.”

Another problem for Fox has been little excitement for the games. BCS participants Louisville, Boise State and Wake Forest simply draw lower ratings than traditional powerhouses like Nebraska, Penn State and Florida State, none of which made the BCS this year.

While Ohio State and Florida are both popular teams, the controversy surrounding one-loss Florida’s selection will not help ratings.

In the eight BCS championship games thus far, the games that have done the best paired undefeated squads like last year’s record matchup between USC and Texas, the most-watched finale since the BCS began.

Finally, the switch from longtime carrier ABC to Fox may have hurt the BCS most of all. Fox doesn’t air regular-season college football games, and thus did not have a great platform to promote the postseason games.

And the network tends to see lower ratings compared with the Big Three when it carries events shared by all the broadcasters, such as the Emmys and Super Bowl, due to distribution, shorter primetime window for promotion, and the relative youth of the 20-year-old fourth network.