Speaking on "The Rachel Maddow Show" on msnbc, Biden said the issue of tax cuts gave Democrats the chance to sharply delineate their differences with Republicans heading into November.
"The alternatives are stark between a Democratic-led House and a Democratic-led Senate, and a Republican-led House and Senate," Biden said.
The vice president said Democrats would take the victories by Tea Party-backed candidates in GOP primaries "very, very seriously."
"I wouldn’t sell short these candidates," Biden said, adding that he expected money to pour into such races as the one for his old Senate seat in Delaware.
In that GOP primary, Christine O'Donnell defeated veteran Rep. Michael Castle. O'Donnell was backed by Tea Party activists and former Alaska Gov. Sarah Palin, but the Republican establishment had publicly fretted that she would be a liability in the general election, in which she'll face Democrat Chris Coons.
Biden had a message for Democrats and progressives: "Get in gear, man."
"You better get energized, because the consequences are serious for the outcome of the things we care most about."
He said that the Obama administration's accomplishments on such issues as health care overhaul, hate crime laws and tobacco regulation would be at risk if the party didn't turn out voters.
"It’s time for our base to take a look and say, hey, man, this opposition is real," Biden said.