A new Field Poll finds Barbara "Call Me Senator" Boxer's prospects for a fourth term less than certain. The Fresno Bee reports:

Former Rep. Tom Campbell has a six-point lead over his closest challenger in the three-way Republican primary to face Democratic Sen. Barbara Boxer, whose popularity has significantly eroded in the past two months, according to a Field Poll released today.

The survey found Campbell leading former Hewlett-Packard CEO Carly Fiorina 28 percent to 22 percent among likely Republican voters in the June 8 primary, while Assemblyman Chuck DeVore had support from 9 percent. But most prospective GOP voters, roughly 40 percent, were undecided.

While Boxer's races have historically been sleepy affairs, the poll indicates that Californians could be in for a barnburner this year. Boxer is in a statistical tie in trial matchups with both Campbell and Fiorina. In January, she had substantial double-digit percentage-point leads over all three GOP challengers.

"Formerly, I would have said this is in the Democratic column, but I would say now it's got to be moved into the tossup column," said Mark DiCamillo, the director of the poll. "There just seems to be a turning of voter opinions. I think a lot of it has to do with the Congress."

As with the Field Poll noting Meg Whitman's slight lead over Jerry Brown, the standard caveats apply. Boxer can be as vicious as anyone. (Just ask Bruce Herschensohn.) And the outcome of the Republican primary is far from assured, especially if Fiorina and Campbell continue clashing.

Somewhere, a demon sheep is bleating.