[cnn-photo-caption image= http://i2.cdn.turner.com/cnn/2010/images/04/21/art.palin.closeup.jpg caption="Sarah Palin is set to star in a new ad for Rand Paul, a candidate for Senate in Kentucky."](CNN) - Sarah Palin's weighing in on the contentious Republican Senate primary battle in Kentucky.
The former Alaska governor is appearing in a new ad for Rand Paul, a physician and the son of former GOP presidential candidate and Texas Rep. Ron Paul. Rand Paul is battling Kentucky Secretary of State Trey Grayson for their party's nomination.
In the television commercial, the narrator says "Paul's conservative approach has the support of Sarah Palin."
The ad then uses an audio clip of the 2008 GOP vice presidential nominee, who backed Paul earlier this year, endorsing the candidate. "He wants limited government. I respect that and I'm proud to support him," Palin is heard saying.
The television commercial follows a radio ad with Palin that's been in circulation in Kentucky for a couple of weeks, according to the Paul campaign
Paul and Grayson are fighting to succeed Sen. Jim Bunning, the Republican lawmaker who announced last summer that he would not run for a third term. National GOP leaders rallied around Grayson at the time. But Paul, a favorite with conservatives and with many in the Tea Party movement, has picked up steam and some recent polls indicate that he leads Grayson in the GOP primary matchup.
Bunning endorsed Paul last week. On Monday, former New York City mayor and 2008 GOP presidential candidate Rudy Giuliani endorsed Grayson, according to the Grayson campaign.
Kentucky's primary is May 18. State Attorney General Jack Conway and Lt. Gov. Don Mongiardo are the top two candidates battling for the Democratic Senate nomination.
Follow Paul Steinhauser on Twitter: @psteinhausercnn