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 FlakeLindsey Graham basks in the impeachment spotlight Kelly, McSally virtually tied in Arizona Senate race: poll The Hill's 12:30 Report — Presented by Nareit — White House cheers Republicans for storming impeachment hearing 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 BarrAndy Hale BarrOn the Trail: Forget the pundits, more electoral votes could be in play in 2020 Mnuchin to lawmakers: 'I'm highly encouraged you will' pass Trump's North America trade deal Kentucky Democrat moves closer to McConnell challenge 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.