Sen. Mike Johanns (R-NE), in his first term in the Senate, unexpectedly announced Monday that he will not be seeking re-election.

The 62-year-old senator and former Governor of Nebraska was swept into power in the very red state in 2008, taking the place of former Sen. Chuck Hagel, who Johanns now supports for Defense Secretary.

He played an instrumental role in congressional "fiscal cliff" talks as a member of the "gang of eight," but found himself frustrated at the chamber's inability to compromise, sources told Politico.

"Words are inadequate to fully express our appreciation for the friendship and support you have given to us over the past three decades," Johanns and his wife wrote in a letter to Nebraskans.

"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. 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."

Johanns added that he and his wife Stephanie, who also has a history serving as a county commissioner and state senator, want "a quieter time with our focus on each other, our family and our faith."

"We look forward to the remaining time in the Senate," the letter concludes. "It is an honor to have served in so many ways over so many years."

Many see Gov. Dave Heineman (R) as a likely successor to Johanns' seat due to the fact that Nebraska's governorship is term limited. Attorney General Jon Bruning (R) is also said to be interested in a run, according to MSNBC.

In announcing his retirement, Johanns joins a raft of senators who've announced the end of their tenure in Congress since the 2012 presidential election. Others include Tom Harkin (D-IA), Frank Lautenberg (D-NJ), Saxby Chambliss (R-GA) and Jay Rockefeller (D-WV).