The Texas Senate GOP primary has now become a battle between Rick Perry and Sarah Palin.

Perry is featured in a new TV ad touting Lt. Gov. David Dewhurst in the May 29 primary, while Palin is supporting former state solicitor general Ted Cruz in a new robo-call encouraging early voting.

The theme from Perry and Palin, both Tea Party favorites: Their candidate is the best to shake up Washington.

Dewhurst, considered the front-runner, is leading Cruz in a new University of Texas/Texas Tribune poll. The GOP primary is a crowded one and includes former Dallas mayor Tom Leppert and sportscaster Craig James.

"David is the one candidate best prepared to make conservative change happen in Washington. Don't let anyone tell you different," Perry says in his ad for Dewhurst.

Palin notes in her automated call that Cruz has been endorsed by the Tea Party Express. She said Cruz is a "conservative you can trust to stand by on principle and change the way Washington does business."

Perry and Palin are friendly, and she endorsed him in 2010 when he faced Sen. Kay Bailey Hutchison in a GOP primary for governor.

Perry has been relatively low key since he dropped out of the presidential race in January, but he's been vocal in support of Dewhurst. Palin has already weighed in on a couple of Senate GOP primaries, backing Indiana's Richard Mourdock and Nebraska's Deb Fischer.

On the Democratic side, former state representative Paul Sadler is leading Sean Hubbard and several other candidates in the University of Texas/Texas Tribune poll. Hutchison is retiring and the state has long been voting GOP in statewide offices.