From a friend from Connecticut with some experience in low-level party politics, a very perceptive person whose judgment I trust:
"In 1980, when I was 20 years old, my parents bought me a three-piece suit. I didn’t have too many occasions to wear a suit, so when I arranged an interview with the State Senate Majority Leader for my college radio station, I put on my suit, walked across the New Haven Green and paid a call on Joe Lieberman. At the time, Lieberman had a reputation as a liberal Democrat. He was running for Congress to succeed Bob Giaimo, a defense-industry-oriented Democrat who had represented the New Haven area (and, as people said at the time, Pratt and Whitney) for years. It was 1980, though – not a good year for liberal Democrats, and Lieberman lost in the Reagan “landslide”.
When Joe Lieberman ran for Attorney General in 1982, the position was a fairly unexciting part-time post, in charge of the attorneys who represented the State of Connecticut in its various dealings. Lieberman was the first full-time A.G., and he quickly transformed the office, using it to grab exposure as a consumer advocate, among other things. He succeeded in forging for himself a public persona that wasn’t ideologically identified, and built up an impressive name recognition around the state. (He so successfully used the AG’s office as a stepping stone that since then the job has been one of the most prized in Connecticut politics.)
In 1988, Lowell Weicker came up for re-election to the Senate. As a liberal Republican (with impeccable credentials as a former member of the Senate Watergate Committee), Weicker had been able to count on his own party and strip off a segment of the Democrats who agreed with him ideologically. This has been a pretty successful formula in Connecticut, but those who have used it have always run the risk of alienating too much of their base. Throughout the 1980’s Republicans talked about mounting a conservative primary challenge to Weicker, but none ever seriously materialized. Instead, Lieberman in 1988 beat Weicker by using that same formula against him. By re-casting himself as a conservative Democrat, Lieberman was able to capture enough disaffected Republicans and independents to defeat Weicker, whom many had considered to be pretty much unbeatable.
The point of this tedious history of state-level politics through the 1980’s is that Joe Lieberman, far from being an ideological beacon to conservative Democrats throughout the years, has, in fact, tacked ideologically as time and circumstances have dictated. He ran for Congress as a liberal and lost. He rebuilt his career as a non-ideological advocate, and then, when it suited him, went at Lowell Weicker from the right.
What I have a hard time figuring out is why he didn’t tack left when circumstances dictated. I suspect that he started to believe his own press notices from the right wingers, and that he really, really wanted that Secretary of Defense job when it was dangled in his direction a while ago.
Ideology doesn’t completely explain Connecticut Democrats’ increasing rejection of Lieberman, though. While some of his positions may be out of sync with many people in his party, those same people would overcome those differences if more of them actually liked him. Unfortunately for him, that doesn’t appear to be the case. When, in the lead up to the convention, he took to the phones calling delegates for support, the question naturally arose – “I haven’t heard from you in 18 years – why are you calling me now?” The 2000 race, when he stubbornly insisted on running for Senate and Vice President at the same time (when Dick Blumenthal could have easily been elected to the Senate and kept the seat Democratic), was the height of selfishness. People remember things like that. Particularly the type of people who vote in primaries."
I also recommend this post by Mark Schmitt.