In his news conference Wednesday morning, President Obama was almost derisive as he dismissed congressional criticism of the military campaign in Libya.

“A lot of this fuss,” he said, “is politics.”

Which was probably not the way to quiet the fuss.

On Capitol Hill on Wednesday, lawmakers said their objections were not simply attempts to score partisan points. They pointed to a pair of recent votes, one in the House and one in the Senate, in which legislators from both parties rejected some of Obama’s arguments on Libya.

“That’s patently just untrue,” Rep. Thomas J. Rooney (R-Fla.) said of Obama’s contention. He referenced a vote last week in the House in which 70 Democrats joined 225 Republicans in voting down a measure to authorize the operation. “Look at the people who have voted to have him come and make the case” for the conflict, Rooney said.

Rooney’s objections were echoed by Rep. Brad Sherman (D-Calif.), who said he agrees with Obama on many issues. In this case, however, Sherman said the president had made an improper end run around Congress and deserved to be called out for it.

“There is a lot of politics in the House, and there may be a few for whom politics” is the main motivator for challenging Obama, Sherman said. “But I think there are a lot of us in the House who are dedicated to the U.S. Constitution and to our oath of office.”

Congressional concern about the Libya operation has focused on a 1973 law, the War Powers Resolution. It says presidents must obtain congressional authorization after sending troops into hostilities abroad.

The deadline for that authorization has passed. The president’s argument is that he doesn’t need it: By his logic, the operation in Libya should not count as “hostilities.”

That, Obama says, is because U.S. forces play a largely supporting role in the NATO-led air campaign against the forces of Moammar Gaddafi; that campaign followed a mandate from the United Nations. Obama has also argued that the conflict does not count as “hostilities” because Gaddafi’s forces are so battered that they pose little threat to American air crews.

Obama repeated those arguments in the news conference Wednesday and implied that congressional objections might serve to strengthen Gaddafi’s resolve.

“We should be sending out a unified message to this guy that he should step down,” Obama said. “And this suddenly becomes the cause celebre for some people in Congress? Come on.”

The Senate Foreign Relations committee heard Tuesday from a State Department lawyer, Harold Koh, who explained the argument about the meaning of “hostilities” in detail. But senators from both parties seemed skeptical. In the end, the committee approved an amended resolution that declared, in essence, that both Koh and Obama were wrong and that the Libyan operation does indeed count as “hostilities.”

The resolution then went on to offer Obama the authorization that he says he doesn’t need. The full Senate must now vote on that measure.

On Wednesday, Sen. Sherrod Brown (D-Ohio), usually a reliable ally of Obama’s, said he thinks the president still has not done enough to convince Congress of his logic on Libya.

“I don’t think the policy’s wrong,” he said, but “I’m not thrilled about it. He should have talked to us more. And ‘us’ [means] the country, not just Congress.”

A spokesman for House Speaker John A. Boehner (R-Ohio) said Obama dodged the original question he was asked at the news conference: Is the War Powers Resolution unconstitutional, as some presidents before him have insisted?

“His refusal to answer a basic question — does he believe the law is constitutional or not — is unacceptable,” said the spokesman, Michael Steel. “Congress and the American people deserve a straight answer.”

The next congressional action could come next month, when the House returns from a July 4 recess. That chamber will take up a bill to fund the Pentagon, and some legislators have said they will seek to strip out all funding for the Libya conflict.

Such a measure seems unlikely to pass the Senate, but it would be a powerful signal that Obama’s arguments have failed to satisfy congressional concerns.

“In addition to not seeking congressional approval, [Obama] hasn’t even sought congressional engagement,” Rep. Michael R. Turner (R-Ohio) said Wednesday. “Congress needs to begin to restrict the president’s operations, since he believes that his power comes from the United Nations and is apparently unlimited.”