By Chris Cillizza
Washington Post Staff Writer
Sunday, September 5, 2010; 9:25 PM
Nearly two weeks removed from Murkowski's stunning defeat by little-known attorney Joe Miller in the Republican Senate primary in Alaska, establishment GOPers are nervous of a repeat in Delaware, where Castle faces 2008 Senate nominee Christine O'Donnell in the Sept. 14 primary.
Castle's resume in elected office in Delaware extends more than 40 years and includes an eight-year stint as governor. So, until recently, it was assumed that he would easily win the primary and the general election to replace appointed Sen. Ted Kaufman, a Democrat.
And political pros still largely dismiss O'Donnell, a marketing consultant who won 35 percent of the vote when she ran against then-Sen. Joe Biden in 2008, as a gadfly. Internal GOP polling conducted last week showed Castle with a margin of nearly 20 points over O'Donnell.
But after Murkowski's loss, there is a desire among Republican operatives to be safe rather than sorry .
In recent weeks, O'Donnell has begun to attract national attention as the next GOP outsider who could upset the party's establishment candidate with help from the "tea party " movement.
Miller's schocking win affirmed the danger to any GOP candidate positioned as a moderate in a small-turnout primary. (Fewer than 110,000 votes sealed Murkowski's fate; Sen. Bob Bennett of Utah lost renomination this year at the hands of 3,500 - or so - Republicans at the state convention.)
A senior Republican operative granted anonymity to speak candidly about the race said Murkowski's defeat was the best thing that could have happened to Castle. "After Alaska, Castle knew he would be next if he didn't run a real campaign - including defining O'Donnell," the source said.
Castle, like Murkowski, was counseled by the national party to go on the attack immediately against O'Donnell, taking advantage of the $2.6 million he had in the bank at the end of July (O'Donnell had $70,000). Unlike Murkowski, Castle listened. He launched radio ads that describe O'Donnell as a "financial disaster." Tough TV spots are on the way, according to knowledgeable insiders.
The state and national parties, after ignoring O'Donnell (and the race) for months, have turned decidedly negative as well, churning out press clips that paint her in the worst possible light.
O'Donnell has done little to help herself. She battled with a local radio show host last week over her previous statement that she had won two counties in her race against Biden: She lost all three of the state's counties, though she came within 272 votes of Biden in Sussex. She has also alleged that political opponents are following her home at night.
"Christine O'Donnell has pretty much been discredited, so I think the primary is in good shape, and this won't be another Utah or Alaska," said Jan van Lohuizen, who is Castle's pollster.
Still, given the number of intraparty upsets this cycle - three senators have lost re-nomination bids, the most since 1980 - it's difficult to write off O'Donnell.
The huge fundraising disparity between the two candidates means O'Donnell needs outside interest groups to wade into the primary on her behalf. The Tea Party Express, which spent upwards of $500,000 on Miller's bid in Alaska, has pledged to spent as much as $250,000 for O'Donnell, although the group's current media buy - approximately $30,000 for radio ads - is far short of that total.
Other major players in national conservative circles seem content to stay on the sidelines, most notably the Club for Growth. It will not get involved for O'Donnell, according to a source close to the group.
Castle, then, should win a week from Tuesday. But the idea that he is politically unassailable is probably gone, handing Democrats at least the glimmer of a surprise victory come November.