Coming just weeks before midterm elections, they said, the intense focus on the matter might further undercut confidence in the government Mr. Obama runs even though it was hardly his fault an intruder with a knife made it into the White House.

“This is an opportunity to make it seem like nobody’s in charge in the Obama administration, even though it’s almost certainly not the case that political appointees could have done anything to change the facts in this situation,” said Matt Bennett, a White House aide under President Bill Clinton and now vice president of Third Way, a political group. “I’m not surprised that they’re doing this.”…

“I do think for a lot of Republican congressmen, this is a twofer,” said Erik Smith, a former House Democratic aide and a campaign adviser to Mr. Obama. “The Secret Service may be in the line of fire, but they’re not the only target.”

Not every Democrat sees it that way. Paul Begala, no stranger to partisan warfare as a longtime adviser to Mr. Clinton, said Republican lawmakers were asking the right questions out of genuine concern. “This is totally on the level,” he said. “They’re acting like real human beings and patriotic Americans.”