After spoiling the plans of the Republican Party establishment in Florida, Nevada, and Alaska, the Tea Party train has pulled into Delaware this week.
Christine O'Donnell, with stout financial backing from the Tea Party movement, leads in some polls over Rep. Mike Castle in the state's GOP Senate primary. Tuesday's vote marks one of the last primary races before November's midterm elections-and it provides a fitting coda on what has been a season-long storyline of veteran lawmakers facing real threats from fresh faces. An O'Donnell primary victory, something considered highly unlikely just a few weeks ago, could add Tea Party muscle within the GOP.
Castle, a popular moderate lawmaker, a former Delaware governor, and the state's lone House member, has long been expected to easily win the GOP slot in the race to fill the Senate seat once held by Vice President Joe Biden.
With Castle's clout, many pundits have predicted that Biden's Delaware's Senate seat looked like an easy pickup for Republicans.
But O'Donnell's recent surge, fueled by new endorsements from conservative ringleaders-including former Alaska Gov. Sarah Palin and Sen. Jim DeMint, R-S.C.-has jeopardized Castle's GOP victory lap.
The matchup pits a social conservative in O'Donnell against Castle, largely socially moderate and fiscally conservative.
O'Donnell has attacked Castle for supporting President Barack Obama's agenda, including voting for the House's cap-and-trade energy bill. Meanwhile, Castle supporters have targeted O'Donnell's personal financial troubles that include past tax issues, overdue college bills, and a troubled home mortgage.
Castle, campaigning in Wilmington on Monday, said the race has become tight because outsiders are hijacking it from Delaware voters.
"This has been a complete out-of-state operation," said Castle, who has spent nearly two decades in the House. "It's not been a local campaign. It's clear they have spent several hundred thousand dollars, to not only take me out, but to take anybody who dares to vote with the other party at any time out."
An O'Donnell win would place her in the ranks of other conservative outsiders who have won GOP Senate primaries this year. Those include Florida's Marco Rubio, Nevada's Sharron Angle, and Alaska's Joe Miller.
"This isn't just about my candidacy," O'Donnell recently told supporters in Dover. "It's about changing the political system. You don't need to be part of the establishment. You don't need to be an anointed one."
Beyond Palin and DeMint, O'Donnell supporters also come from an unusual camp: state and national Democrats. Doubting O'Donnell's ability to win a general election in the largely liberal state, Democrats would rather avoid facing Castle's name recognition and popularity.
Polls show that O'Donnell would begin the general election race down 11 points to leading Democratic nominee Chris Coons. Meanwhile, polls show that Coons would begin behind Castle if those two were matched in the general election.
If those numbers hold, the intra-GOP battle over the party's ideology could make it more difficult for Republicans to take control of the Senate. Republicans must win 10 seats in November to become the majority party.
That is why some conservative groups like Dick Armey's Freedom Works have withheld throwing their support behind O'Donnell. Delaware's GOP chairman, Tom Ross, has actively campaigned against O'Donnell, calling her both kooky and delusional. But this has only stoked the fire of such groups as the Tea Party Express, which has poured more than $250,000 into the race's final days. This is helping O'Donnell, 41, make up a sizeable campaign cash deficit: Over the summer Castle had $2.6 million in his campaign coffers while O'Donnell had a mere $20,000 in her campaign account.
O'Donnell, who lost badly to Joe Biden in her 2008 campaign for the Senate seat, founded Savior's Alliance for Lifting the Truth (SALT) in 1996 and also served as a spokesperson for Concerned Women for America.
In 2005, O'Donnell filed a gender discrimination and wrongful termination lawsuit against her former employer, Delaware-based conservative group Intercollegiate Studies Institute. But she eventually dropped the $6 million suit.
Despite these controversies, Tuesday's primary outcome will test if the Tea Party's reach extends to disaffected voters in more left leaning states.