Pres. Bush's refused to endorse the GOP candidate in Connecticut. His silence was a tacit endorsement for Lieberman. Between that and the Pres. and VP going around praising Lieberman's WOT record didn't help the GOP in Connecticut at all.
And don't try to claim that Lieberman didn't get a lot of high-level GOP support.
"Lieberman has raised $15.6 million, drawing substantial support from out-of-state sources — particularly from financial service executives in New York City and lobbyists. Lieberman has continued to raise funds in the waning days of the campaign, including a $12,100 contribution from New York Mayor Michael Bloomberg, a Republican, and $5,000 from former Sen. Alfonse D'Amato, R-N.Y." From Senate race: Shrill, nasty, expensive