CONGRESS BRISTLES whenever anyone suggests it is irrelevant, but to tell the truth, there are times when it wishes it were. Like now. Like when war looms, a determined president says we must go forward -- and people tell congressmen they have to do something.

"We've gone from being functionally useless in their eyes to being their only savior," says Rep. Dennis Eckart, a Democrat just back from a recess in his district in Ohio. "They rush up to me at shopping malls and say, 'You've got to stop the president from taking us into war.'"

There is a way, of course, of stopping presidents. Congress can vote to forbid him to go to war. They could have done that when the crisis began on Aug. 2 or when the first 200,000 U.S. troops were sent or at the dispatch of the second 200,000. They can still do it.

Actually, Congress doesn't need to exert itself in this regard, because the Constitution has given it the sole right to declare war. Alas, Congress is too insecure to lean on the sacred document which brought it into being. It can, as House Majority Leader Richard Gephardt mentioned recently, simply cut off funds for a war being waged without its permission. Or finally -- and this is too dreadful for them to think about even if someone like Saddam Hussein were in the White House -- Congress can impeach a wayward president.

But Congress is a body much given to wringing hands when it is not shaking them, and it has no idea what to do. It can take a vote on the United Nations resolution, which imposes the deadline of Jan. 15 on Saddam to exit Kuwait. Passage would be, they observe glumly, "tantamount to a declaration of war," which is the very thing they wish to avoid.

On the other hand, they may do nothing. Why pass something while the last call for peace is under way, as Secretary of State James Baker is flying to the Middle East and then to a parley in Switzerland with Iraq's foreign minister? They could look awfully foolish -- not to say wimpy -- if Baker brings home the bacon while they are bleating, in innumerable amendments, about the course being followed.

If they urge caution, they invite comparison with a lion-hearted president who has no doubts whatever about the moral, political and military rightness of his policy. George Bush, who was frantic over a televised encounter with Dan Rather during the 1988 campaign, is utterly calm over a potentially bloody confrontation with an armed and dangerous character he calls "a madman." Several months ago, when Congress was growling and snapping, its leaders went to the White House threatening to bite his newly offensive policy. He whipped out an Iraqi report detailing Saddam's "joy" in U.S. dissent. Congress came out with its tail between its legs. But last week, he didn't threaten them, which could have been even more unnerving.The administration had its worst moment during last month's hearings by the Senate Armed Services Commitee and Chairman Sam Nunn (D-Ga.), an unexpectedly staunch advocate of giving the sanctions time to work. He was not subject to the usual Republican charge that Democrats are reluctant to use force. Republicans, except for Vice President Dan Quayle, who tripped over a couple of discrminatory golf clubs, are not especially gung ho. After his hearings, Nunn returned the microphone to the president.

Rep. Louise Slaughter (D-N.Y.) says the president's insistence on the need to repel "naked aggression" has no resonance in her district, which is the home of Terry Anderson, the longtime hostage supposedly held by Syria, one of our new allies in the gulf. "Terry Anderson being handcuffed to a wall is about as naked as aggression gets, and Bush's friend Assad hasn't let him out."

Rep. Barbara Kennelly (D-Conn.) finds a contradictory constituency. Its letters and phone calls register 99 percent opposition to military action, but in polls it comes out being 70 percent in favor of it.

Rep. Edward J. Markey (D-Mass.) thinks that voters may be trying to help the president in bluffing Saddam Hussein. They are repelled by Saddam, but they don't want to rush into getting him out of Kuwait with American lives.

The confusion and uncertainty has reached foglike density. Bush's insistence on personalizing the contest with Saddam and his dismissal of the effectiveness of sanctions make politicians more nervous than they ought to be.

It's a time when a principled resignation -- such as that of Eduard Shevardnadze -- would help more than anything. If a high-level official like Colin Powell or Dick Cheney were to turn in his portfolio and say that the president is on the wrong track, that we are indeed not prepared for desert warfare, that sanctions could work, we could pull back from the brink. Congress might even find the courage to say no offensive action unless provoked.

Mary McGrory is a Washington Post columnist.