First of all, the latest poll numbers I've been able to find show that in a three way race, Lamont and Lieberman are
neck and neck. Lieberman is certainly not the runaway favorite. That poll was taken on July 20, and I'm not aware of anybody else taking any new polls of the general population since then.
Secondly, there are a lot of things that can happen in between now and November. I don't necessarily think Lamont will win the general election. What I do know is that we don't have a clue who will win at this point. This primary changes a lot of things.
For one thing, as a result of this primary, Ned Lamont has received the support of Hillary Clinton, Evan Bayh, Barbara Boxer and John Edwards. Yeah yeah, I know, I don't like Hillary either. But that kind of support will count for a lot in Connecticut. Lamont has also already received the support of institutional lobbying groups like Connecticut unions. Lieberman's campaign funding will take a huge hit from this primary. Americans don't like losers.
Also, the turnout for the primary was something like 50% which is literally record-breaking. With that many Democrats supporting Lamont, Lieberman would have to win a sizable majority of unaffiliated voters in Connecticut which is not a sure thing at all since "independent" in Connecticut usually means "too liberal for the Democrats."
And then there's the question of Schlessinger. The smartest thing Republicans could do is get him to drop out because his support base would largely break for Lieberman over Lamont. But there's no indication yet that he will do that.
Anyway, the Democratic Party establishment did in fact see this coming, and they gave a lot of support to Lieberman. For whatever reason, Lamont won anyway. And I would also point out that as recently as late June, Lamont was
trailing Lieberman in polls. We've got twice as much time from now until November, and there's simply no telling which way the polls will go in that amount of time.