Dennis Welch, political editor for 3TV in Phoenix, has new poll numbers in U.S. Senate showdown between Democrat Richard Carmona and Republican Jeff Flake:

The results of a surprising new poll in the U.S. Senate race were released Wednesday showing Democrat Richard Carmona beating his Republican rival.

The survey, which was conducted by a GOP-friendly firm, shows Carmona holding a 5-point edge over Jeff Flake.

Heading into the race, Flake was considered the heavy favorite to win in a state where Republicans hold a comfortable registration advantage over Democrats.

We don't know much about the poll (Welch doesn't identify who did it because the source is top-secret), so there's every reason to be skeptical about it—or at least consider it an outlier.

But as I wrote in this TW's print edition, surveys have shown a tightening race and the campaigns are trading blows.

Flake is now up on TV with this ad:

The intent, obviously, is to link Carmona to Obama, given that Obama's numbers aren't, at the moment, all that good in Arizona.

Meanwhile, Carmona is on the air with an ad that stresses his independence—which, if you know Rich Carmona, is pretty accurate assessment of the guy. Like him or not, it's tough to dismiss him as a rubber stamp.

Where is all this going? Well, polling guru Nate Silver still has Flake as the favorite here in Arizona, with a 70 percent chance of victory as of today.

But Silver notes today that the momentum is shifting across the country in favor of Democrats in Senate races:

The Democrats’ chances of controlling the Senate have increased to 79 percent in the forecast, up from 70 percent on Tuesday.

Had we run the model a month ago, based on polls through Aug. 19, the Democrats’ chances of maintaining Senate control would have been listed at just 39 percent.

The velocity of the change is unusual. Although Senate races in different parts of the country can sometimes move in the same direction, there was never quite this rapid a shift in our Senate forecasts in 2008 or 2010.

The forecast model is not doing anything particularly fancy; it’s just that an overwhelming number of Senate polls recently have shown the Democratic candidates’ standing improving.

The big question: Will that wave move into Arizona this year?