You're figuring the two Independents (Lieberman and Jeffords) are Donks?
Jeffords retired. He was replaced with Socialist Bernie Sanders.
Lieberman is a liberal Democrat. He's only an "independent" because the Democrats fielded an even more liberal opponent. He's also stated he'll be voting with the Democrats. Jeffords was a RINO before declaring himself an "independent" in a self effacing effort to have the "deciding vote".
The Republicans supported Lieberman in favor of the Republican candidate who didn't have any hope of winning and the Democrat challenger who prefers a "cut and run" approach. Politics make strange bedfellows.