Despite a slim margin separating the candidates, Attorney General Jon Bruning called challenger Pete Ricketts to concede the Nebraska GOP gubernatorial primary Tuesday.

"Sometimes you fight hard and come up short," he wrote online.

I have called @RickettsForGov to concede. Sometimes you fight hard and come up short. Thank you to all my supporters.

— Jon Bruning (@JonBruning) May 14, 2014

With 91.6 percent of precincts reporting, Ricketts led Bruning 26.3 percent to 25.6 percent and 1,525 votes separated the two candidates.

Ricketts, the former chief operating officer of Ameritrade, Inc., is the son of Joe Ricketts, founder of the Omaha-based online brokerage firm TD Ameritrade, Chicago Cubs owner, and billionaire GOP donor.

Tuesday's face-off between the two was something of a re-match. In the 2012 GOP Senate primary, Bruning was the frontrunner until Joe Ricketts dumped a huge amount of money in a last-minute superPAC ad buy on behalf of Deb Fischer, who won the primary and the general election.

The race drew a number of high-profile endorsers for Ricketts, 49. Vice President Dick Cheney and Sarah Palin, as well as possible 2016 contenders Wisconsin Gov. Scott Walker, Indiana Gov. Mike Pence, Paul Ryan, and Ted Cruz all backed Ricketts.

Nebraska Gov. Dave Heineman, who is term limited, backed Bruning. With Nebraska a deep red state, Ricketts now becomes the favorite for November's gubernatorial election.