Carmona is one of Democrats' best hopes for taking over a Republican-held seat this year to retain and perhaps strengthen their majority. The candidate was personally recruited by President Obama, and his tenure as surgeon general under George W. Bush has helped to burnish his crossover appeal in a state that leans Republican.

And Carmona spokesperson Elizabeth Kenigsberg said that the new poll indicates that he's competitive with both Republican and Democratic voters.

"This poll proves what we've been saying all along. This race is winnable because Rich Carmona is a unique candidate with broad and bipartisan appeal," she said.

However, Flake is well-known in the state, and still largely well-liked, with 44 percent of voters viewing him favorably while 35 percent say they view him unfavorably. And if he can successfully attach Carmona to Obama, he has a chance of leaping ahead in the race — Romney holds a 9-percentage-point lead on the president.

And the poll indicates that there's still room to make such a tactic stick — a full 49 percent of voters say they're still unsure about Carmona, indicating there's still room for Flake to define the candidate. That's in part why he launched, just a little over a week ago, a website and online ad labeling Carmona "Rubberstamp Rich" for his support of Obama's policies.

Flake spokesperson Andrew Wilder said the results of the poll were unsurprising.

"The Flake campaign has always expected this to be a close race -- that's why Jeff is working hard earn the trust and votes of Arizonans," he said.

Thus far, though, it's hard to tell the actual state of the race, as few independent polls have been conducted.

The PPP poll was conducted from Sept. 7-9 among 993 likely Arizona voters and has a margin of error of 3.1 percentage points.

--This post was published at 3:13 p.m. and updated at 4:45 p.m.