Republicans sent a message of "no moderates need apply" in their Senate primary on Tuesday night, Vice President Biden said.

Biden said he found it "tough to explain" how conservative insurgent candidate Christine O'Donnell managed to beat Rep. Mike Castle in a Republican Senate primary,

"the truth is that it’s real tough for the Republican Party. It’s kind of hung on a shingle," Biden told MSNBC's Rachel Maddow in an interview to air this evening. "You know, no moderates need apply.  It’s sort of spawned a tone in politics that is not helpful to getting things done. And we’re a moderate state."

Biden said that if the state's 185,000 Republican voters had all turned out to vote in yesterday's primary, instead of the small number who did, then Castle, a popular longtime congressman and former governor, would be the Republican candidate for the vice president's old seat today.

The vice president made reference to O'Donnell on Monday during a fundraiser in Philadelphia, but hadn't commented directly on her Tea Party-fueled candidacy. He did express thanks, though, for Democrat Chris Coon's entry into the race. (Biden's son Beau, the state attorney general, had for a time also considered entering the race.)

"And we thank God we have a really first rate candidate. This guy is solid.  He is honorable. He’s incredibly well educated. He’s done a great job running the largest county," Biden said. "This is a really solid guy. And so, that’s the good news for us."

The vice president also lashed out at other conservatives, including former House Speaker Newt Gingrich (R-Ga.), who suggested President Obama was "foreign" in temperament.

"I mean, there is such a desperation on the Republican side to pander to the lowest common denominator," Biden said.