Slate’s David Weigel had his own spin on the decision, describing Lieberman’s move as “part graceful exit, part hit-the-road-before-they-burn-my-house-down.”

We can give the man some time to explain why he’s doing this, but let’s not lose sight of the obvious: He was going to lose if he ran. One of the last polls on a potential 2012 race, an October 2010 survey by Public Policy Polling, gave Lieberman an abysmal 31 percent approval rating. Twenty-four percent of voters said they’d re-elect him, to 66 percent who said they wanted to vote for someone else. In trial heats, Lieberman came in third in potential three-way contests; he lost by double digits to possible Democratic opponents.

… Lieberman turned everybody off and broke a series of promises. If you were a Democrat who supported him, you heard him promise to endorse the party’s 2008 presidential candidate, then you watched him endorse John McCain. If you were a Republican who supported him, you heard him say he couldn’t vote for the health care bill in December 2009, because of the Medicare buy-in. You might have even waved pro-Lieberman signs, as some people I met at a Tea Party rally in D.C. did at that time. Then you watched him cave once the buy-in came out.

Weigel’s Slate colleague Alex Pareene was harsher still, questioning the recent achievement most liberals counted as a point on the board for Lieberman.

If this is true, his work repealing “don’t ask, don’t tell” was less an attempt to appeal to Democratic primary voters than it was the potential start of a last-ditch effort to be remembered for something other than the term “Joementum.” (To be fair, Lieberman has always supported the rights of gay people to serve openly in the armed forces—though “always” having supported things has not stopped him from changing his mind on plenty of other policy issues.)

Many are questioning the timing of Lieberman’s decision, rumors of which came just a day after former Connecticut secretary of state Susan Bysiewicz announced she would run in a Democratic primary for the seat. CNN’s Ed Henry reported that a “Lieberman aide stressed that the Senator made his own decision some time ago and it was not influenced by Bysiewicz’s announcement Tuesday or any other maneuvering.”

Susan who? Well, those feverish race-watchers at Politico have some background for you:

In attempt to shield herself from criticism about her political savvy, Bysiewicz released internal polling data that showed her defeating several Democratic primary rivals, Lieberman and 2010 GOP Senate and gubernatorial nominees Linda McMahon and Tom Foley.

This will be the third statewide run the 49-year-old Bysiewicz has attempted during the past two years. After forming an exploratory committee for governor in 2009, she switched to run for attorney general after former Sen. Chris Dodd announced his retirement and Attorney General Richard Blumenthal launched a Senate bid.

Her campaign for attorney general ran into problems and ended last spring when the state Supreme Court ruled her ineligible to hold the office because she never tried a case as a lawyer.

The National Republican Senatorial Committee swiftly unloaded background documents on Bysiewicz Tuesday, under the bold headlines “ethical problems” and “embarrassment.”

The Times’s own feverish race-watcher, Nate Silver, discusses what might happen with Lieberman’s seat (as well as retiring North Dakota senator Kent Conrad’s) at his FiveThirtyEight blog. Bysiewicz is not the only one to look out for, according to Silver.

Democrats, meanwhile, have a fairly deep bench in Connecticut, including several candidates who have been preparing to run for some time on the assumption that Mr. Lieberman might run as an independent, or could lose a Democratic primary. Susan Bysiewicz, until recently Connecticut’s Secretary of State, has already declared for the race, and at least one of the state’s U.S. Representatives—most likely Chris Murphy, who represents the 5th district—is likely to run as well. The primary will be hard-fought—and annoying to New York City television viewers who don’t like seeing political commercials from neighboring Connecticut creeping into their broadcasts of the Yankees game—but Democrats should emerge with a competent candidate.

Competent candidate? Well, they all start out that way…

Joel Meares is a former CJR assistant editor.