Jeffords abandoned the Republican party and gave the Democrates control of the Senate. Liberman was abandoned by the Democrate party which did not affect control of the Senate. There is a BIG difference there and if you can't understand that you don't under stand politics.
Having a left wing freak in the Senate makes for better laugh lines! Unfortunately it makes for great danger too.
Near as I can tell there is a BIG difference because you say so. In either case it's a question of party loyalty. Of course the Democrats are going to support the nominee of their party, regardless of years of support of Lieberman. If Chaffee loses his primary in Rhode Island and announces he's running as an independent then who do you think the Republicans would get behind? He, too, could make the case that the Republican party abandoned him but he wouldn't get a whole lot of sympathy and even less support from the party. In any case it's not going to make a bit of difference. Assuming Lieberman wins in November I give the whole independent nonsense 6 months before he's back in the fold as a Democrat once again.