Probably the single most exciting poll of the season thus far. Not only does it suggest that one of the most loathsome Democrats in Congress is really, truly vulnerable, but if even California’s in play then retaking the Senate might be doable after all.

Midterm fee-vah — catch it!

California Republican U.S. Senate candidate Carly Fiorina has increased her lead over Democratic incumbent Barbara Boxer to five percentage points according to a new CBS 5 KPIX-TV poll released Thursday, which also shows gubernatorial candidates Democrat Jerry Brown and Republican Meg Whitman in a dead heat…

The poll results indicated Fiorina’s support was essentially unchanged among men and women, young and old, white and Hispanic while Boxer had lost small ground among men, younger voters, and independents.

The poll also showed Fiorina tripling her lead in the Central Valley, from seven points one month ago to 21 points in this latest poll.

According to the crosstabs, Fiorina wins 27 percent of the black vote, trails among Hispanics by just six points, and crushes Boxer among indies by 17. There’s no GOP slant in the sample either; it splits 44D, 34R, and 23I. Now here’s where I give you the obligatory eeyore caution: Survey USA’s a respected pollster but they’re the only ones to show Fiorina with a lead this year. Their last poll had her up two points and a Pajamas Media poll taken in June had the race even, but literally everyone else — including Rasmussen — has Boxer ahead by anywhere from five to nine points. So consider these new numbers not so much an answer as a question: Just an outlier, or a leading indicator of a trend in the race? Rasmussen’s last poll did show Fiorina closing in, but only ever so slightly (a two-point gain). Keep this on your radar screen, then, with an eye to confirmation via the next round of polls. Just a little tremor happening in California, or is this the Big One?

Meanwhile, WaPo just moved two more Senate races from “lean Democratic” into the “toss-up” column. Hmmmmm. Exit question: Could the bump for Carly be part of a backlash to the Proposition 8 ruling? She denounced it after it was handed down, but per Survey USA’s analysis, it looks like she hasn’t gained any support so much as Boxer has bled some. And given that part of the bleeding is coming from gay-friendly young voters, I’m thinking … no, probably not the Prop 8 decision. But stay tuned.