As of the Aug. 8 filing deadline, Carmona had over $1.75 million cash on hand; Flake reported just over $1.705 million cash on hand.

The Flake campaign pointed out that the Republican candidate outraised Carmona this reporting period, taking in a little less than $50,000 more than the Democrat, and that part of the reason Carmona had overtaken Flake was because of the protracted Republican primary in the state. Flake faces a challenge from local businessman Wil Cardon, though the lawmaker is expected to win the nomination handily on Aug. 28.

"Our cash on hand numbers are neck and neck. That's pretty embarrassing for them when you consider that Carmona has had all year, uncontested to amass a war chest, while Flake has been locked in a high-dollar primary battle," said Flake spokesman Andrew Wilder.

But the Carmona campaign insists that the large amount of cash Flake had to lay out to overcome the challenge from Cardon indicates Flake isn't a strong contender for the seat.

"Congressman Flake is a 12-year incumbent who needed to spend millions of dollars to beat a primary opponent he once led by 50 points. Congressman Flake has been in this race for a year longer than Dr. Carmona, and these reports show a clear trajectory for both candidates: Carmona is rising, and Flake is sinking," Carmona spokesman Andy BarrAndy BarrYellen's House testimony a 'lovefest' compared to past visits The Hill's Whip List: 36 GOP no votes on ObamaCare repeal plan A guide to the committees: House MORE said.

--This article was posted at 6:07 p.m. and updated at 7:08 p.m. to reflect the correct amount by which Flake outraised Carmona.