In Tuesday's Delaware primary, the tea party movement may inflict its most devastating wound yet to the Republican establishment.
With an assist from Sarah Palin, tea party activists in Delaware are trying to defeat the Republican candidate with the best chance to win Joe Biden's old Senate seat and nominate instead a candidate Republican leaders say has no chance of winning the general election in November.
Rep. Mike Castle is considered a slam dunk to capture Joe Biden's old Senate seat. Castle is a pro-abortion rights, pro-gun control Republican who often works with Democrats. Those traits have helped make him the most popular Republican in a state that leans heavily Democratic; Castle has twice been elected governor and was elected as Delaware's sole representative in the House nine times.
But Castle's moderate politics have enraged tea party activists and given Christine O'Donnell an opening.
"The Republican Party has lost its way," O'Donnell said. "They get behind candidates like my opponent who don't even support the Republican platform, who continue to support the Democrats' agenda, lock-step-and-barrel."
Castle hasn't had a seriously contested primary since 1992. He said he's confident this time, but acknowledges he could go down.
"This one's been difficult, not only because I have an opponent with whom I disagree adamantly on a number of issues but is also being funded by the Tea Party Express people, which is totally an out of state circumstance," Castle said.
The group Tea Party Express, which also supported the primary campaigns of Sharron Angle in Nevada and Joe Miller in Alaska, said it will spend nearly $200,000 boosting O'Donnell's primary challenge.
This one, however, may be the most bitterly divisive Republican primary yet. Republican leaders say an O'Donnell victory would destroy the state party and pretty much ruin any GOP chances of capturing Biden's old seat.
"I have no doubt if she by some miracle became the nominee she would lose the seat by unprecedented numbers," Delaware Republican Party chairman Tom Ross said.
O'Donnell, who has also been endorsed by Sen. Jim DeMint, R-S.C., and the NRA, called that "Republican cannibalism," which she said is an indication of just how out of touch with their voters and desperate main stream Republicans have become.
The Delaware Republican party has been issuing almost daily press releases attacking O'Donnell.
One recent release highlighted a Rasmussen poll showing Castle carrying a double-digit lead over Democrat Chris Coons in the general Senate race, 48 percent to 37 percent. When Coons and O'Donnell are matched up, Coons leads O'Donnell by a 47 percent to 36 percent margin.
O'Donnell said she remains confident that voters see her as the real Republican choice.
"There's a tidal wave coming here in Delaware and my campaign is riding it," she said. "My opponent is drowning in it."
Democrats, meanwhile, are salivating at the possibility of an O'Donnell victory Tuesday because if she wins, Democrats are suddenly favored in Delaware. A Democratic victory in Delaware would make it virtually impossible for Republicans to capture a majority in the Senate.
Whatever happens in Delaware, tea party Senate candidates have already toppled the choices of the Republican establishment in six states this year.
You can watch the extended clip of the interview with Rep. Mike Castle and read the transcript here.