Tomorrow marks the end of a particularly brutal primary season for Senate Republicans, and another upset is in the making: a Public Policy Poll released this weekend shows insurgent Christine O'Donnell tied within the margin of error with party-backed Rep. Mike Castle. O'Donnell was recently endorsed by Sarah Palin, who made an issue out of "establishment attacks" on O'Donnell. 

Many of those attacks, though, are in the form of panicky warnings from the Professional Right, quite apart from the party, which views O'Donnell as a disaster of a candidate, someone who could prevent Republicans from picking up a Senate seat that would have easily, otherwise, been theirs. Matt Lewis, Patrick Ruffini, John McCormack, and others have ruminated to this effect. The state Republican Party chairman said that O'Donnell was unworthy of being elected "dog catcher." The Weekly Standard's John McCormack posted a tough investigative piece that calls O'Donnell's motives into question.

Predictably, the harsher Republicans have resisted O'Donnell, the more excited the Tea Party Express has become about her candidacy. This is not simply a case of insurgents versus the party, however: the NRA endorsed O'Donnell too, and many of her opponents have supported plenty of the insurgent candidates who defeated NRSC-hand-picked candidates in other Senate races. (I don't think a single one of O'Donnell's professional GOP critics, aside from the NRSC, would oppose Ovide Lamontagne winning in New Hampshire on Tuesday.)

Mike Castle can still win this primary, because about 30,000 people are going to vote. But the Tea Party Express, and Sarah Palin's robo-calls, have turned out plenty more than 30,000 voters before.

If O'Donnell wins, Democrats believe that, with the right injection of money and enough targeted GOTV, Chris Coons, the Democrat who ran instead of Attorney General Beau Biden, can win the seat.