Richard Lugar's tea party challenger stood Wednesday morning outside the Indianapolis home the Republican U.S. senator sold decades ago to make the case his opponent no longer has much to do with the state he represents.

State Treasurer Richard Mourdock's election-year charge is just the latest in a series of them levied by an unlikely alliance of Democrats and conservatives who have joined forces to argue the veteran senator has spent so much time in Washington, D.C., he has lost touch with Indiana. Both sides sense political vulnerability from the state's senior senator, once considered untouchable.

An Indiana tea partier filed voter fraud allegations against Lugar last December, claiming his official residency is now in Virginia and that he has committed fraud each time he has voted since selling his Indianapolis home in 1977. Hoosiers for Conservative Senate, a tea party umbrella group backing Mourdock, planned to petition Gov. Mitch Daniels Thursday to act on the complaint.

"I don't think he's been qualified for ballots in past years and of course again this year," said Monica Boyer, HFCS co-chair.

Boyer said she planned to ask Daniels to call a hearing of the state election commission to consider the allegations. Daniels, who has been mentored by Lugar throughout his career, dismissed that idea Wednesday.

During his news conference outside Lugar's former home, Mourdock called Lugar's residency in Virginia a violation of Article 1 of the U.S. Constitution, which mandates that a senator be an "inhabitant" of the state they are representing when elected.

While nearly all members of Congress have living arrangements in the Washington, D.C., area, most also own homes or a rent apartments in the states they represent. Lugar typically stays in hotels when he returns to Indiana and no longer has a physical address in the state.

"We decided that when we have a campaign theme about the senator no longer being in touch with Indiana, the perfect place to kick off this campaign is here, in front of the house he once owned," Mourdock said.

Lugar spokesman David Willkie did not immediately return an email Wednesday from The Associated Press seeking comment.

Two Indiana attorneys general have maintained that elected officials serving in Washington do not need to live or maintain a home in Indiana to be a legal resident of the state.

"There is no requirement that a person maintain a house, apartment, or any fixed physical location," said then-Attorney General Linley Pearson in a 1982 opinion provided to Lugar ahead of his 1982 race. Attorney General Greg Zoeller has supported Pearson's interpretation of state law.

Conservative activist Greg Wright filed a complaint with the Indiana Election Commission in December alleging voter fraud by Lugar and his wife Charlene. But the commission, which weighs whether or not candidates make it on the state ballot, has not scheduled a hearing on the complaint.

Daniels said he wouldn't force the election commission to hear the complaint.

"Both the constitution and the statute are clear that (Lugar) is qualified as he's been for all his previous elections. We're going have a good, competitive election but he ought not try to end it on a technicality that really isn't legally valid," Daniels said.

Daniels cut his teeth time working with Lugar in the Indianapolis mayor's office and then followed him to Washington in 1977 as his chief of staff.