Cardon's campaign said the ads revealed that Flake and his allies are desperate and "hell-bent on using an onslaught of attack ads to distract voters from the truth."

Cardon has attempted to impugn Flake's credentials as a conservative, accusing him of supporting amnesty for illegal immigrants and of advocating for higher taxes and greater spending. But the Club for Growth, which endorsed Flake in February, will argue in its ads that it is Cardon whose leadership would bring about more taxes and spending.

"Wil Cardon is an imposter," the narrator says in one of the ads. "Says he's a conservative, but he helped lead a campaign for a $9 billion tax increase. Cardon: not a conservative."

The other television ad knocks Cardon for being a member of the Urban Land Institute. The Club has accused that group of being too liberal and of supporting higher energy taxes.

"The lies in these ads are laughable," said Cardon spokeswoman Alyssa Pivirotto. "The truth? Wil Cardon opposes increased gas taxes and cap-and-trade energy taxes. Saying Wil supports such measures because he's affiliated with the Urban Land Institute is like saying Jeff FlakeJeffrey (Jeff) Lane FlakeHillicon Valley: EU hits Google with record B fine | Trump tries to clarify Russia remarks | Sinclair changing deal to win over FCC | Election security bill gets traction | Robocall firm exposed voter data Overnight Defense: More Trump drama over Russia | Appeals court rules against Trump on transgender ban | Boeing wins Air Force One contract | Military parade to reportedly cost M Senate resolution backs intelligence community on Russian meddling MORE, as a member of Congress, is personally responsible for ObamaCare."

The winner of the August primary between Flake and Cardon will face Democrat Richard Carmona, who is running unopposed for his party's nomination. Carmona spokesman Andy BarrGarland (Andy) Hale BarrMidterms will show voters are tired of taking back seat to Wall Street Lawmakers demand answers from Mnuchin on Trump tariffs Overnight Health Care: Trump officials want more time to reunite families | Washington braces for Supreme Court pick | Nebraska could be next state to vote on Medicaid expansion MORE said it wasn't surprising the Club felt nervous and needed to shore up its candidate.

"Congressman Flake's lead is evaporating and his supporters are hitting the panic button," said Barr.

But the Club for Growth said the group wanted to make its case before early voting starts in Arizona, adding that it was important not to stand by idly while Cardon misrepresents his record.

"Arizona is a deeply red state. President Obama is not going to compete there," said Club for Growth spokesman Barney Keller. "Despite all protestations from Democrats to the contrary, the Carmona campaign is the equivalent of spitting into a hurricane."

Watch one of the ads:

- This post was updated at 2:27 p.m.