Polls suggest that two-thirds of Americans approve of President Obama's decision to launch airstrikes in Libya, but Operation Odyssey Dawn has not gone over so well on Capitol Hill. Obama is facing scathing criticism from both sides of the aisle, with some even suggesting he should be impeached for sending U.S. warships and planes into battle without getting the approval of Congress first. Here, five major groups that have attacked Obama over the Libya intervention:

1. Liberal congressmen
Withering criticism has come from the most liberal of Obama's fellow Democrats. Rep. Dennis Kucinich (D-Ohio) is leading the charge, saying that putting members of the Air Force and Navy in harm's way is "a grave decision that cannot be made by the president alone." Kucinich said Obama violated the Constitution by failing to seek congressional approval, and that "would appear on its face to be an impeachable offense." Many commentators have scoffed at the notion that the president was out of line.

2. Libertarian congressmen
That hasn't stopped Kucinich's conversative counterparts from pursuing a similar line. Only Congress has the authority to declare war, says Rep. Ron Paul (R-Texas), and firing cruise missiles and dropping bombs on Moammar Gadhafi's forces is clearly "an act of war." "The no-fly zone is unconstitutional because Congress has not authorized it," he says.

3. Republican leadership
GOP leaders in both the House, like Speaker John Boehner, and the Senate, like Sen. John McCain (R-Ariz.), have lambasted Obama over Libya. The complaints have come even from GOP hawks: Rep. Ileana Ros-Lehtinen (R-Fla.) condemned Obama for "deferring to the United Nations and calling on our military personnel to enforce the 'writ of the international community,'" while McCain is worried Obama waited too long to save the Libyan rebels.

4. Moderate senators
One worrying sign for Obama is that moderate senators in both parties have protested. Sen. Richard Lugar (R-Ind.), ranking minority member of the Senate Foreign Relations Committee, has frequently backed up the administration, but not this time. "If we're not on the edge of an active war, we are close enough that the president really ought to have a debate in the Congress," Lugar told CNN. Sen. Jim Webb (D-Va.), a former Navy secretary, said flatly: "This isn't the way that our system is supposed to work."

5. Liberal celebrities
Not all of the complaints are coming from Congress. Former Green Party presidential candidate Ralph Nader is calling Obama a "war criminal." Liberal filmmaker Michael Moore says Obama is a hypocrite, and should return his Nobel Peace Prize. Moore also tweeted sarcastically, "We've had a 'no-fly zone' over Afghanistan for over 9 years. How's that going? #WINNING!"

Sources: New York Times (2), Politico, TPM, Gather, Telegraph, Los Angeles Times, Tribune, Richmond Times-Dispatch, CNN