(CNN) – Republican Senate candidate Richard Mourdock's campaign released a new radio ad Monday, hammering six-term incumbent Sen. Dick Lugar of Indiana and adding to the thickening tension between the two candidates in the final two weeks of the primary race.
The 60-second spot directly takes on recent Lugar attacks ads that target Mourdock as a tax fraud, highlighting the ads as "misleading," "an exaggeration" and " straining the facts."
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"Have you seen those attack ads from Dick Lugar against Richard Mourdock?" the ad's narrator says. "Dick Lugar is so desperate to stay in Washington that he's resorting to false negative attacks."
In a scathing commercial last week, Lugar's campaign pointed to an error on Mourdock's recent tax returns claiming thousands of dollars in extra homestead deductions-a mistake Mourdock said he had attempted to fix years ago but said his paperwork had been lost by the state, resulting in a delay.
The Marion County Auditor's Office has since taken responsibility for not removing the error when requested by Mourdock.
Mourdock, the state's treasurer, has the support of major tea party and other conservative groups-both state and national-hoping to unseat Lugar, the longest serving Republican in the Senate.
In Mourdock's radio ad released Monday, the campaign bashed Lugar for living outside the state since he first became senator in 1976, repeating a major rallying cry for critics of the veteran senator.
"During those 36 years in Washington, Dick Lugar lost touch with Hoosier conservative values and became Obama's favorite Republican," the narrator says.
Lugar, who lives in Northern Virginia, beat back challenges of his residency after the Indiana Election Division ruled in favor of Lugar's situation. A loophole in the state's election law allows individuals to maintain residency as long as they're serving in the state's capacity.
The Mourdock radio ad Monday also criticized Lugar for confirming President Barack Obama's Supreme Court picks of Sonia Sotomayor and Elena Kagan. The National Rifle Association has criticized Lugar's votes for the two nominees, as well.
Responding to the commercial, Lugar's campaign described the spot in a statement as a "negative, deceptive ad to distract Hoosiers from the growing list of questions plaguing (Mourdock's) campaign."
Team Lugar specifically addressed the Supreme Court attacks, saying the senator "proudly led conservatives in the confirmation fights" for Chief Justice John Roberts and Justices Antonin Scalia, Clarence Thomas and Samuel Alito.
"Senator Dick Lugar has factual rebuttals and answers to all the questions raised, while Richard Mourdock appears unable to answer the growing list of troubling questions facing his campaign," the statement read.
While Mourdock represents the first major threat ever to Lugar's re-election, some in the GOP establishment have rushed to Lugar's side, including Indiana's popular governor Mitch Daniels, who appeared in ad released Sunday for the senator.
Recent polls indicate the two candidates in a dead heat. While Indiana doesn't hold its primary until May 8, early voting has been underway across the state since March 24.