CHARLOTTESVILLE, Va. — At the start of their debate here last week, the Republican challenger for Congress, State Senator Robert Hurt, paused only long enough to thank the League of Women Voters before ripping into Representative Tom Perriello for voting for “government-run health care.” Mr. Hurt returned to the topic seven times over the next hour, despite being asked only once.

If Mr. Hurt was reading from his party’s playbook, so was Mr. Perriello, a freshman Democrat scrapping to survive in the centrist Fifth Congressional District, which spans central and southern Virginia. He emphasized that the health law had preserved the private insurance system, and that he had already been thanked by constituents who can “go to bed at night not having to worry” that they will be bankrupted by disease. Then he asked for a chance to improve an imperfect law.

“This doesn’t change overnight,” Mr. Perriello said, “but we are moving in the right direction.”

That interplay has been replicated across the 2010 campaign, with Republicans largely keeping Democrats on the defensive about the Obama presidency’s signature domestic achievement. While clearly secondary to economic concerns, the continuing debate over health care has remained prominent in numerous races for the House and Senate.

President Obama, who typically has not campaigned for individual House members, plans to make an exception on Friday by appearing here with Mr. Perriello, the White House said Monday.