The senior senator from Nebraska, Mike Johanns, announced his retirement today. It’s a major surprise. He’s only 62 years old, and he’s serving his first term. He’s a giant in Nebraska politics, having served as the mayor of Lincoln, the governor, and as one of George W. Bush’s secretaries of agriculture. He could probably remain in the Senate for as long as he wants to, but he has decided to leave. In a letter to his constituents, he gave no specific reason for his decision not to run for reelection. He pointed out that he’s spent thirty-two years in public service and that that is enough.

Now, this is pure speculation, but I think it is not unlikely that Johanns wants out of Washington because of how Chuck Hagel is being treated by his colleagues in the Senate. Johanns replaced Hagel in the upper chamber, and they are friends. Johanns announced early on that he would vote to confirm Hagel as Secretary of Defense, and he was one of only four Republicans to oppose a filibuster of Hagel’s nomination (Orrin Hatch voted ‘present’).

No doubt, there are plenty of other reasons for members of Congress to be frustrated and disgusted, but there is a straw that will break every camel’s back. Perhaps watching Sen. Ted Cruz (R-TX) accuse Hagel of taking money from the North Koreans was that straw. Maybe it was watching the way McCain disrespected his former buddy. I doubt that Johanns will ever talk about it, but he can’t be happy about how Hagel has been treated.

I have a feeling that things have grown too toxic on a national level for the normally polite Nebraskans. First Hagel quit, then Ben Nelson, and now Mike Johanns. The state is certainly conservative, but it also has the only unicameral and nonpartisan state legislature.