The Club for Growth and Rep. Trent Franks (R) are currently engaged in a proxy war over the Arizona Senate GOP primary.

Franks has endorsed real estate investor Wil Cardon, while the club is backing Rep. Jeff Flake in the GOP race to succeed retiring Sen. Jon Kyl (R).

Franks appeared in a new Cardon television ad calling a recent ad from the club “absolutely false.”

The club responded swiftly.

“The facts in our ads are entirely accurate: Wil Cardon did support a massive tax increase, and Cardon is a leading member of a liberal organization that wants to raise gas taxes and backs a cap-and-trade energy scheme,” Club for Growth Communications Director Barney Keller wrote in a statement. “Trent Franks is a good man and it’s a shame that he is allowing his personal bitterness at the Club for Growth PAC’s support of Jeff Flake over him in the U.S. Senate race to cloud his judgment about liberal Wil Cardon.”

At issue is Proposition 400, a 2004 extension of a half-cent transportation sales tax in Maricopa County. A spokeswoman in the Cardon camp told Roll Call that Cardon does not support tax increases from Capitol Hill but does support voters’ right to approve such action via referendum.

Roll Call rates this race as Leans Republican. Former Surgeon General Dr. Richard Carmona is the presumptive Democratic nominee.