Speaking at a fundraiser Thursday morning for Sen. Barbara Mikulski (D-Md.), Vice President Joe Biden said victories in GOP primaries by Tea Party backed candidates should motivate Democrats this fall.

"Maybe the best thing to happen to us lately is the Tea Party wins," said Biden. "Maybe it’ll shake some of our constituency out of their lethargy." 

Tea Party-backed candidates have won a string of upset victories in Republican primaries this year with the most recent coming in Delaware. Conservative commentator Christine O'Donnell shocked longtime Rep. Mike Castle (R-Del.) and now trails Democrat Chris Coons by a wide margin in the general election.

On the ground in competitive states and districts, Democrats have increased their focus on the Tea Party with some seeing it as the best motivating message for Democrats this fall.

Polls have showed a large enthusiasm gap between Democratic and Republican voters ahead of November's midterm elections. 

The most recent Gallup tracking poll, which Biden referenced during Thursday's event, did give Democrats a one-point edge on the generic ballot question, but found a 19-point enthusiasm gap. Just 28 percent of Democrats said they were "very enthusiastic" about voting in November, compared to 47 percent of Republicans who said they were. 

Still, the vice president reiterated his confidence that Democrats would retain their majorities in both the House and Senate after November's midterm elections. 

“I guarantee you we’re going to have a majority in the House and a majority in the Senate. I absolutely believe that,” Biden said. 

While Mikulski's race isn't looking like a competitive one this fall, Biden is embarking on a fundraising swing for more vulnerable congressional Democrats, reports the Wall Street Journal. The vice president is expected to hit close to 60 competitive races between now and November.