GAINESVILLE, Fla. — As virtually any member of the Florida football team will agree, the margin for error is gone. It vanished with a missed extra point two weeks ago in a 31-30 loss to Mississippi.

The loss dropped the Gators (4-1 overall, 2-1 in the Southeastern Conference) out of the top 10 in the polls and Tim Tebow off the list of Heisman Trophy favorites, after winning the award as a sophomore last year.

All that is about to change — one way or another — tonight, when Florida hosts LSU (4-0, 2-0) in a matchup of the last two national championship teams.

"It is an absolute must-win for Florida," said CBS analyst Gary Danielson, who will work the game. "They have the schedule that favors them. They only have one more road game in the SEC this year and it's a manageable game at Vanderbilt. Vanderbilt is a good team, but it's better than going to Alabama or Georgia. This is a schedule that is manageable and winnable. If they win this game, they still could make a run at the national championship because they will get to play LSU, Alabama and Georgia, and probably LSU or Alabama again, which will be good enough to get there."

Tebow agrees it's a vital game.

"It's huge," he said. "I think it's huge more so than just even a loss in the SEC. Just for momentum, just for confidence in people, just for defending The Swamp again, I think it's huge."

The Tigers bounced the Gators out of SEC and national title hopes last October in Baton Rouge with a 28-24 win. LSU was a perfect 5-for-5 on fourth downs and only led after scoring the final touchdown of the game.

Those fourth-down plays have been playing on video screens all over the UF football facilities this week.

"It's playing in the weight room," Gators defensive coordinator Charlie Strong said. "It's playing in the locker room. It's playing in the hallways so guys get to see that tape and they see that game. That game is constantly running."

That game was played in front of a sold out crowd at Tiger Stadium. This time, it's a packed house at Florida Field.

"This year it's going to be a big change," Florida linebacker Brandon Hicks said. "Everybody's going harder, everybody's going 100 mph and everybody's got a chip on their shoulder."

The Gators have some issues to correct. Two weeks ago, it was three fumbles in the loss to Ole Miss, UF's last home game. Last week, it was 110 yards in penalties in a 38-7 win at Arkansas. Both were season-highs.

"It's like turnovers," said Florida coach Urban Meyer of the penalties, "You address it, then you coach it, you show it on film. There is not a better group of players than our offensive line. We have a good bunch of guys that understand the value in limiting penalties. It will be corrected."

LSU is second in the conference in rushing offense (206.5 yards a game) and is second only to Florida's 36 points per game in scoring offense (35.5). If the Gators fall behind, because of mistakes, it will be a tough road back.

"We're starting an eight-week stretch here that will determine how good we are as a team," Tigers coach Les Miles said. "I can only tell you that playing well at Florida will determine a lot on how I would rank bits and pieces of our football team."

If the Gators have an advantage, it could be throwing the football. Tebow hasn't put up the same numbers as a year ago, but he still leads the SEC in passing efficiency with a 148.0 rating. LSU is eighth in the league in passing defense, giving up 191.8 yards a contest.

Miles disputes that Tebow isn't playing well.

"I have to be real honest with you, struggles to him don't seem to be struggles to me," Miles said. "He plays pretty darn well and plays well in key situations for them. I think, like anything, when things don't go well there's got to be somebody that takes the blame and certainly the quarterback gets his undue share. He's a team leader of their team and everybody responds to him. I think he's doing a very good job."

The Tigers' Charles Scott leads the conference with 133.8 yards rushing per game. Miles likes his offensive line play. At the same time, the Gators' rush defense has been hot and cold. So the game could come down to how well LSU runs the football and controls the game clock vs. how many big plays Florida is able to come up with to exploit the Tigers' secondary.

For the Gators, the time for excuses or mistakes is over. It's their chance to save the season. And for the Tigers it's a chance to make theirs even better.

"Everybody is hyped," said Maurkice Pouncey, the Florida center, "from the fans down to the trainers. Everybody is hyped."

Contact David Jones at djones@floridatoday.com.