A new TV ad in the U.S. Senate race.

Club for Growth, a conservative Republican PAC, is going to spend $500,000 in a campaign accusing U.S. Senate candidate Wil Cardon of  being a “conservative imposter.”

The first part of the campaign focuses on two 15-second TV ads (links here and here) and a 60-second radio ad. Cardon, a businessman from Mesa, is running against U.S. Rep. Jeff Flake in the Republican primary for U.S. Senate. Bryan Hackbarth and Clair Van Steenwyk are also on the Republican primary ballot.

Club for Growth, which advocates for lower income taxes and replacing the tax code, has endorsed Flake in this race, and Flake has brought in nearly $599,000 in campaign contributions from people who earmarked the donations through the Club for Growth Pac.

The group’s criticism of Cardon is based on Cardon’s support of a $9 billion tax increase and his membership in the Urban Land Institute, which they say is a liberal group that supports increased gas taxes and cap and trade energy taxes.

The radio ad calls Flake the “real conservative.”

Cardon sent out a press release in response to the ad, calling what he says are “lies” in the ads laughable. Cardon opposes increased gas taxes and cap-and-trade energy taxes, and has signed “Americans For Tax Reform” pledge to never raise taxes, the press release points out.

“Falsely claiming Wil Cardon supports tax increases because he’s affiliated with the Urban Land Institute is like saying Jeff Flake, as a member of Congress, is personally responsible for 'Obamacare,'” the press release says. “Clearly these are desperate times at Flake headquarters and for the out-of-state wealthy special interests and lobbyists who support him. Lies and attacks, of course, are a hallmark of a career politician Arizona voters cannot and should not trust.”

The latest poll from Public Policy Polling showed Flake with a 22-point margin over Cardon. That’s still a big lead for the six-term Congressman, but smaller than the 49-point margin he had on Cardon in a February poll done by Public Policy Polling.

Cardon has put in $4.2 million of his own money into his campaign, producing several attack-style TV ads about Flake’s stances on immigration reform, his taxpayer-funded travels and his flip-flopping on issues.

The presumptive Democratic U.S. Senate candiate, Richard Carmona, meanwhile, is trying to use the disputed Republican primary to give his own campaign a higher public profile.

Carmona’s spokesman, Andy Barr, Tweeted that the big buy from Club for Growth shows Flake is worried.

“Congressman Flake’s supporters are starting to panic. Wouldn’t be attacking @Cardon2012 if Flake’s numbers were strong,” Barr Tweeted.

Flake’s spokesman, Andrew Wilder, responded to Barr on Twitter.

“No, a panic button is something pushed when a single mom hears banging on her door in the middle of the night,” Wilder Tweeted, referring to an accusation made by Cristina Beato, the former assistant secretary in the Health and Human Services Department.

Beato, who was Carmona’s supervisor during his stint at U.S. Surgeon General, says Carmona banged on her door at her house in the middle of the night, screaming about issues the two disagreed on. The Carmona campaign denies the accusations.

Tucson doctor David Ruben is also on the Democratic ballot in the Aug. 28 primary.

Club for Growth endorsed Flake earlier this year, saying he has been a “tireless champion of economic freedom” and that he was a perfect successor to Sen. Jon Kyl.

The group also highlighted how Flake opposed the worst policies of the current Obama administration as well as the Bush administration, citing earmarks, bailouts and the prescription drug entitlement as examples.

Flake has received nearly $599,000 in donations that were earmarked through Club for Growth from January 2011 through March 2012, Federal Election Commission reports show.

That’s 20 percent of the $3 million in individual contributions of $200 more that Flake has brought in.

Stay tuned to the Pueblo Politics blog throughout 2012 for news, updates and information about Arizona politics. You can follow Arizona Daily Star reporter Brady McCombs on Twitter by clicking on his name.