In an interview with an Israeli television network, McCain said Obama has "encouraged our enemies" by effectively punting his decision to Congress. He and fellow Republican Sen. Lindsey Graham of South Carolina have threatened to vote against Obama's authorization if it is too limited.
On the other end of the spectrum, an unusual coalition of foreign policy isolationists, fiscal conservatives and anti-interventionists in both parties opposes even limited action for fear that might draw the United States into another costly and even bloody confrontation.
The White House request to Congress late Saturday speaks only of force to "deter, disrupt, prevent and degrade" the Assad regime's ability to use chemical weapons.
"I think it's a mistake to get involved in the Syrian civil war," said Sen. Rand Paul, R-Ky.
Echoing that sentiment, Sen. Chris Murphy, D-Conn., questioned, "Does a U.S. attack make the situation better for the Syrian people or worse?"
Paul expected the Senate to "rubber-stamp" Obama's plan, while he said it was "at least 50/50 whether the House will vote down involvement in the Syrian war." Inhofe predicted defeat for the president.
Despite the intense gridlock in Congress over debt reduction, health care, immigration and other issues, some lawmakers were more optimistic about the chances of consensus when it came to a question of national security.
Rep. Peter King, R-N.Y., who criticized Obama for not proceeding immediately against Assad, said he'd vote "yes" and believed the president should be able to build a House majority over the next several days.
"At the end of the day, Congress will rise to the occasion," added Rep. Mike Rogers, R-Mich. "This isn't about Barack Obama versus the Congress. This isn't about Republicans versus Democrats. This has a very important worldwide reach."