Sen. Richard Lugar (R-Ind.) released a new attack ad Monday, accusing his chief GOP primary rival, Indiana state Treasurer Richard Mourdock, of selling out to "D.C. outsiders." Lugar, who has held his Senate seat since 1977, is one of several Republican incumbents targeted by the Tea Party in this year's primary contests.

The ad features people who appear to be average Indiana voters wondering to what extent Mourdock, if elected, would be beholden to backers from outside the Hoosier State.

"If he were senator, heaven help us, because Mourdock won't," says one voter in the ad.

The Howey/DePauw Indiana Battleground Poll released last week showed Lugar leading Mourdock by just 45 to 37 percent, effectively moving the primary race into the toss-up category.

Mourdock responded to Lugar's new ad by telling The Hill, "It's amusing that he's been in D.C. 36 years and he's trying to portray me as a D.C. insider. That's ironic, to put it mildly."

Lugar's opponents have made his personal residency a major issue in his reelection bid. As the Associated Press reported last week:

He fumbled questions about the address on his driver's license: an Indianapolis home he sold in 1977. He had to switch his voter ID to his farm in Indianapolis after the local election board ruled last month that he couldn't vote using the 1977 address. Lugar, who owns a home in Virginia, also repaid the U.S. Treasury $14,700 last month that his Senate office paid for his hotel stays in Indiana.

Indiana's GOP primary is scheduled for May 8.

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