Ryen Russillo and Danny Kanell discuss Las Vegas bookmakers' concerns about Iowa with a lot of bettors putting money on the Hawkeyes as a longshot to win the national championship. (1:43)

Alabama and Clemson lead a group of perennial powers atop the odds in Las Vegas to win the national championship, but several bookmakers are more concerned about Iowa as the college football season kicks off.

The Crimson Tide, at 6-1, are the favorites at the majority Las Vegas sportsbooks, but not all of them.

Clemson is the favorite at William Hill. Clemson, LSU and Michigan are listed as co-favorites, each at 6-1, at MGM's books.

Senior quarterback C.J. Beathard is one of 13 starters returning this season for Iowa, which has emerged as a worrisome national title long shot in Las Vegas. AP/Charlie Neibergall

At the Westgate SuperBook, more money has been bet on LSU to win the national championship than any other team. Michigan is second.

Ohio State and Florida State also are receiving strong support from bettors and are in the top tier of favorites at the majority of books. But no team could do as much damage to some books as upstart Iowa.

"Iowa's taken some good money," Johnny Avello, executive director of race and sports at the Wynn, said. "They are our worst liability right now, but we have a whole season to get off them."

The Hawkeyes opened as a 100-1 long shot to win the national championship but have been bet down to 25-1 at the Wynn. Iowa is also the worst-case scenario at the Westgate and for Las Vegas sportsbook operator CG Technology, where Iowa begins the season with better odds than Stanford (30-1), Oregon (40-1) and Michigan State (80-1).

The Hawkeyes return 13 starters, including senior quarterback C.J. Beathard, from last year's team that went 12-2 and lost 45-16 to Stanford in the Rose Bowl. Iowa has only one team currently ranked -- Michigan -- on its schedule. The Wolverines visit Iowa City on Nov. 12.

Clemson quarterback Deshaun Watson, Stanford running back Christian McCaffrey and LSU running back Leonard Fournette have the best odds to win the Heisman Trophy. Watson is 9-2 at the Westgate, followed by McCaffrey and Fournette at 5-1.

Louisville quarterback Lamar Jackson, who accounted for eight touchdowns in the first half of the Cardinals' 70-14 opening win over Charlotte on Thursday, began the week at 100-1 to win the Heisman Trophy at the Westgate.