Lt. Gov. David Dewhurst (File)

AUSTIN (May 14, 2012)—Texas Gov. Rick Perry has made a radio ad defending Lt. Gov. David Dewhurst in his run for the U.S. Senate.

Perry rejects conservative critics who have called Dewhurst a moderate who supported raising taxes.

National tea party organizations say Dewhurst is not conservative enough.

In the radio ad, which began airing on Monday, Perry calls the groups opposing Dewhurst "Washington insiders" using "doubletalk" to mislead Texas voters.

Perry has courted tea party groups in the past.

The anti-tax group Club for Growth said it will spend $1 million on ads targeting Dewhurst.

The National Tea Party Express has also endorsed former Texas Solicitor General Ted Cruz.

Other major candidates include former Dallas Mayor Tom Leppert and former broadcaster Craig James.

Early voting began Monday.