"I think what will probably happen is that this will be hammered on by the opposition. Whoever is running against you is just going to nail you for it," said Donald F. Norris, chairman of the public policy department at the University of Maryland Baltimore County.
The Sun reviewed home addresses for all 53 Republican and Democratic candidates who filed for Congress by Wednesday's state deadline, including incumbents.
Frederick County, where Bartlett lives.
Krysztoforski challenged Bartlett for the GOP nomination in 2010, when the district included his home, and won 16 percent of the vote.
"I want to stay in the 6th District," he said. "I identify with the people of the 6th District."
For others, the district is less important than the competition.
George English, a Silver Spring Democrat, filed this month to run against Rep. Steny Hoyer, a Democrat from Southern Maryland. But Hoyer's 5th District never crosses into English's Montgomery County.
"I deliberately chose the 5th District," English wrote in an e-mail. "I want to challenge the incumbent there."
Sun reporter Annie Linskey contributed to this article.