I'm having a hard time seeing how this is a victory for the Democratic party. Now, when it's Lamont vs Lieberman and the Republicans are allowed to vote as well, you think Lamont will have the edge? Nope. And then you'll still have a mainly democrat senator; the only change will be that he doesn't count as a D anymore when you tally up the senate. Remember Jim Jeffords? A 50-50 Senate is much different animal than a 50-49 one. Might not Lieberman change affiliation for the good of the party? He could. But he also might remember how the Democrats treated him in this primary and tell them to pound sand.
The Democrats had a primary and the Republicans won it.