Politicians, especially United States senators, don’t tend to give up power easily. Imagine Lyndon Johnson voluntarily leaving the Senate leadership — especially at a moment when his party seemed poised to win the majority.

So it was a surprising moment when Tennessee Republican Lamar Alexander went to the Senate floor Tuesday to announce that he would not seek another leadership post when his term as GOP conference chair expires in January. In the most striking phrase, Alexander said the move “will liberate me to spend more time trying to work for results on issues that I care the most about.”

A former governor, education secretary and two-time candidate for his party’s presidential nomination, Alexander described himself as a “very Republican Republican.”

That may be, but to understand Alexander’s sometimes uncomfortable fit into the role of chief message strategist for Senate Republicans, consider:

● When the Senate was on the brink of breakdown over threats to filibuster judicial nominees, Alexander helped forge the Gang of 14 agreement to avert the so-called nuclear option. He was one of nine Republicans voting to confirm Supreme Court Justice Sonia Sotomayor.

● Although opposition to the individual mandate has become a litmus-test issue for Republicans, Alexander signed on to a far-reaching health reform plan, crafted by Oregon Democrat Ron Wyden and then-Sen. Robert Bennett (R-Utah), that required individuals to obtain insurance.

● Despite his party’s no-new-taxes orthodoxy, Alexander agreed to the bipartisan Gang of Six debt-reduction plan that called for a mix of spending cuts and — pause here for horrified gasp — new tax revenue.

As Alexander told me when I went to see him the day after the announcement, the Gang of Six’s formula “was basically to reform the tax code, lower the rates and to use some of the savings to reduce the debt. I thought that made common sense as a general principle. In the Simpson-Bowles case, it was like 20 percent of the revenues that were created by lowering the rates went to reduce the debt. I think I could persuade 99 out of 100 people walking down the street in Maryville, Tenn., that that made common sense.”

In Maryville, perhaps, but not in the Republican caucus.

At a time when crafting bipartisan legislation is viewed by some as consorting with the enemy, Alexander is working on clean-air legislation with Delaware Democrat Tom Carper and on nuclear waste disposal with Democrats Dianne Feinstein of California and Jeff Bingaman of New Mexico.

“If I could get a 100 percent Republican solution, I’d do it,” Alexander told me. “But you can’t do that in the Senate. It requires 60 votes. So some of us have to be willing to try to get results that include coalitions.”

The cynical interpretation of Alexander’s move is that he saw the handwriting on the wall and knew he would lose a bid to move up in the party hierarchy.

The No. 2 position, whip, is opening with the retirement of Sen. Jon Kyl (Ariz.). In going for that slot, Alexander would have been competing against John Cornyn (Tex.), who dispenses campaign checks — and thereby collects some chits — as head of the Senate GOP’s campaign arm.

But Alexander’s decision also underscores the frustration endemic among his colleagues about too many meaningless quorum calls and too little serious legislating.

“Most senators are here to offer amendments, vote, advocate and get a result,” Alexander said. “The idea that we go through a whole week on this useless discussion about disaster aid this week, with limited opportunities for amendments — that is genuinely frustrating to most members of the Senate.”

Listening to Alexander talk about the issues he’d like to work on — unglamorous but important efforts such as increasing funding for national laboratories or finding a safe way to dispose of nuclear waste — offers a jarring contrast to the shrunken federal role envisioned by some in his party.

His vision of controlling entitlement spending under control is to open fiscal space for investments in higher education or infrastructure improvement. He would junk existing energy subsidies — but invest the money in research and development for clean energy.

I left thinking that the Senate with a liberated Alexander could be a better place indeed.