Updated 1:08 p.m. | Nebraska Sen. Mike Johanns, who was a safe bet to win a second term in 2014, announced Monday that he would forgo re-election.

“With everything in life, there is a time and a season. At the end of this term, we will have been in public service over 32 years,” Johanns wrote in an email to constituents co-signed with his wife, Stephanie. “Between the two of us, we have been on the ballot for primary and general elections 16 times and we have served in eight offices. It is time to close this chapter of our lives.”

Republicans are heavily favored to hold the open seat in the conservative state.

Nebraska GOP Gov. Dave Heineman is term-limited from seeking re-election in 2014 and is considered a likely candidate in the race to replace Johanns. The governor has the right of first refusal, and if he runs he would be the “400-pound gorilla” in the race, according to state GOP strategist Sam Fischer. Most other Republicans would likely defer to him.

“My guess is that he’s not going to be in a rush” to make a decision, Fischer said of Heineman.

If Heineman doesn’t run, the GOP faces the prospect of a crowded and bruising primary. “There’s no shortage of people,” Fischer said of a field of prospective GOP candidates.

The state has three Republican congressmen — Jeff Fortenberry, Lee Terry and Adrian Smith — but Fortenberry is viewed as most likely to run, according to Fischer.

The two men who lost to now-Sen. Deb Fischer in the 2012 primary are likely to look at the race: state Attorney General Jon Bruning and state Treasurer Don Stenberg. Also mentioned is businessman Pete Ricketts, who lost to Democratic then-Sen. Ben Nelson in 2006.

Stenberg was the quintessential tea party candidate in 2012 — he had the backing of the Club for Growth, FreedomWorks and the Senate Conservatives Fund, and they invested heavily on his behalf in that race. Most strategists at the time said that he had a 20 percent ceiling in the field with Bruning and Deb Fischer, and that proved true for the perennial candidate.

Ricketts lost big in 2006 — by 28 points. But the Omaha World-Herald noted in 2009 that his failed 2006 race did nothing to damper his political organizing, headlining the story, “Loss Didn’t Cool Ricketts’ Jets.” He has deep pockets and his father, TD Ameritrade founder Joe Ricketts, put six figures into TV ads against Bruning and for Fischer during the 2012 GOP primary.

Nebraska is an extremely inexpensive state when it comes to buying TV ads, and that creates opportunity for the unexpected. As a result, Bruning and Stenberg (and their outside group supporters) bludgeoned each other in the 2012 primary, providing a window for Deb Fischer to sneak up and win the primary.

Johanns is the fifth senator to announce his retirement this cycle. To see which other members are leaving Congress or looking to move up, check out Roll Call’s Casualty List.