After three straight routs to open SEC play, Auburn is a touchdown favorite at LSU, where it has not won since 1999.

No. 10 Auburn (5-1, 3-0 SEC) is a 6.5-point favorite against LSU (4-2, 1-1 SEC) on Saturday (2:30 p.m. CT, CBS) in Baton Rouge, according to VegasInsider.com.

The point spread fluctuated on Sunday, officially opening with Auburn favored by nine points.

An online sportsbook opened with Auburn favored by 6 and then 6.5 at minus-200, but within 30 minutes moved to 7, 7.5, 8, 8.5 and then 9.5 at minus-150. The line settled at Auburn minus-6.5 at minus-100 by 6:30 p.m. CT.

It's a big shift in the spread from preseason betting lines for the game at two Las Vegas casinos.

The South Point casino had LSU favored by 4.5 points when it opened lines on May 29 and the Golden Nugget had LSU favored by 7 on June 22.

Auburn has won two of the last three meetings in the series, including 18-13 last year, but has not won in Baton Rouge since the 1999 Cigar Game.

LSU, which holds a 28-22-1 edge in the all-time series, is coming off a 17-16 win at Florida but lost its last home game to Troy.

James Crepea is an Auburn beat reporter for Alabama Media Group. Follow him on Twitter @JamesCrepea.