Until this point, Heineman had not said who he supports, in the race to fill the seat he's held for ten years.
Heineman has worked closely with Bruning, who has served as attorney general for the past 12 years.
Meanwhile, Pete Ricketts has picked up more endorsements in his bid to be governor. Ricketts has already been supported by national figures like Sen. Ted Cruz, Gov. Sarah Palin, and Gov. Scott Walker. Now he has been endorsed by Rep. Paul Ryan, former vice presidential nominee.
Ricketts responded to the latest endorsement for his opponent.
“While I appreciate Gov. Heineman’s service to the state, this decision is no surprise - Jon is a status quo candidate and a career bureaucrat. The choice is now crystal clear: status quo and ‘auto pilot’ versus reform and growth," Ricketts said.
Bruning and Ricketts are in a crowded Republican field, that includes a pair of state senators -- Beau McCoy and Tom Carlson, plus State Auditor Mike Foley, along with Omaha tax attorney Bryan Slone.