I’m completely mystified. Here’s what the poll of polls looks like:

And here’s Survey USA this afternoon:

In the Republican primary for US Senator, support for former Hewlett Packard CEO Carly Fiorina is up sharply in the past 2 weeks, from 24% on 05/10/10 to 46% today 05/24/10. Fiorina’s support has more than doubled among women, seniors, Hispanics, the less educated, and in the Inland Empire. During these 2 weeks, Former Congressman Tom Campbell’s support dropped 12 points, from 35% on 05/10/10 to 23% today 05/24/10…

SurveyUSA interviewed 2,700 California adults 05/21/10 through 05/23/10. Of them, 2,311 were registered to vote. Of the registered voters, 612 were determined by SurveyUSA to be likely to vote in the 06/08/10 Republican Primary; 716 were determined to be likely to vote in the 06/08/10 Democratic primary. Early voting began two weeks ago, 05/10/10.

If you’re thinking 612 is too small a sample and therefore bound to produce unreliable results, think again: Rasmussen used 500 likely voters in his latest poll of the Arizona gubernatorial race. Survey USA is a reputable pollster too, so there’s no reason to think that the books were cooked here. And yet … how could Fiorina’s support double in just two weeks? Palin’s endorsement came back on May 6, the same day as the Senate primary debate, but if Fiorina got some huge bounce out of that it should have shown up (at least partly) in the last Survey USA poll taken between May 6 and May 9. It didn’t. Carly was floundering at 24 percent; Campbell led with 35 percent and DeVore was actually a point better than he is today at 15 percent.

Assuming the poll is accurate-ish and not some wild outlier, the only explanation I can come up with is undecideds breaking hard for Fiorina for whatever reason. In the poll two weeks ago, 23 percent were undecided. Today’s it’s only 11 percent, with virtually the entire difference having now broken for Carly along with a huge chunk of Campbell’s support. Any reason why that would be? All I can figure is that Campbell was hurt by the emphasis on Israel at the debate, and since DeVore appears to be a lost cause, fencesitters have decided on Fiorina as the best combo of viability and principle. Any theories?