INDIANAPOLIS (AP) — A campaign stop for Rep. Luke Messer in his bid for Senate involves traveling from his family's home in suburban Washington back to Indiana, where aides say he typically stays overnight with his mom.

Although living outside the state is hardly a first for members of Indiana's congressional delegation, past elections signal Messer's address could complicate his plans to win the Republican primary and ultimately unseat Democratic Sen. Joe Donnelly next year.

Towering figures in Indiana politics, including former Democratic Sen. Evan Bayh and Republican Sen. Richard Lugar, were toppled in recent years after struggling to explain whether they still lived in the state. Others took major steps to head off the issue, including former GOP Sen. Dan Coats, who rented and later purchased a home in Indiana, while selling off one elsewhere.

Then there's Messer. His family lives in McLean, Virginia, keeps a vacation house in Dandridge, Tennessee, yet sold their home in Indiana two years after his election to Congress in 2012. They now say a two-bedroom house Messer co-owns with his mom in Greensburg is the family's Indiana residence.

One of his chief primary rivals, fellow Rep. Todd Rokita, has already seized on that as a line of attack.

"Luke Messer doesn't live in the state — I do," Rokita told Indianapolis-based WXIN-TV in July. "I'm accountable to voters and taxpayers here. I live among them every week."

For his part, Messer says he relocated his family in order to stay close. He was raised by a single mother and wanted to be engaged in his three kids' day-to-day lives, unlike his own father. Plus, his family's move to Virginia was well known and never a secret, he said.

"I am proud to serve our state, but being a dad comes first," Messer said in a statement Wednesday. "My opponents think that's gonna cost me this election. If it did, I would never regret it."

Still, changes made to the mortgage on the family's Virginia home in August 2016 suggest he's aware it's a liability.

Messer and wife, Jennifer, switched the home's designation from a "principal" residence to a "second home," records show. His campaign says the change was made on their bank's recommendation while refinancing the house.

But the switch also coincides with a rough patch in Bayh's bid for his old Senate seat, when he faced widespread ridicule for forgetting his Indianapolis address during a TV interview.

Additionally, Messer's other home in Tennessee, which overlooks a lake at the foot of the Great Smoky Mountains, also carries a "second home" designation, according to records.

Messer's campaign says he sleeps at his mom's house in Greensburg when staying overnight in the state. He's listed on the deed and pays a portion of the mortgage. The address appears on his driver's license and is where he is registered to vote.

"It's Luke's house," said campaign manager Chasen Bullock.

But as recent as May, he was not on the water bill and is not listed as the "borrower" on a second mortgage taken out on the home, records show.

Jennifer Messer, an attorney, lists the home as her in-state business address. However, voting records show she's no longer registered in Indiana and hasn't cast a ballot since her husband's 2012 election.

With two bedrooms and approximately 1,500 square feet, it's also far smaller than the roughly 2,700 square-foot McLean residence where Messer, his wife and three children live, when basements are factored in, records show.

"When the entire family is home (in Indiana), they stay at Luke's brother's because there's not enough room at the Greensburg house," Bullock said.

A memo from a Rokita strategist declared that Messer's "decision to sell his home in Indiana" will be "the death knell of his campaign."

Over the summer, Messer's Wikipedia page was mysteriously edited to include a section titled "Residency controversy." Messer blames Rokita, who denies responsibility.

"Todd Rokita believes he can keep his own political career alive by attacking Luke's family. He underestimates the fundamental decency of Hoosiers," Bullock said.

Charles Taylor, director of the Bowen Center for Public Affairs at Ball State University, says residency attacks are a way for Rokita to distinguish himself when both candidates have similar voting records.

"Fights within the family are often the bitterest," Taylor said.

In addition to Bayh, Lugar's 36 years in the Senate came to an end in 2013 after it was revealed during the primary that he was registered to vote at an Indianapolis home he hadn't lived at since the 1970s.

As a campaign tactic, though, it hasn't always worked.

Coats was attacked in 2010 by Democrats and Republican state Sen. Marlin Stutzman. But Coats still won after he acknowledged that he was house hunting in Indiana and planned to sell a home in North Carolina.

Six years later it was Stutzman, by then a congressman, who was targeted during a GOP Senate primary for moving his family to Virginia. Rep Todd Young beat him and later defeated Bayh to become Indiana's junior senator.

Purdue University political science professor James A. McCann says President Donald Trump's vilification of Washington and the political culture that surrounds it could play into Rokita's hand — at least in the short term.

"I think a lot of the Republican primary electorate in this state is going to be primed and susceptible to these messages," McCann said.