A really good political metaphor can go both ways. One season's description of success need only be altered slightly to serve as the next season's gloss on disarray.

Take Teflon.

"What's happened is the Teflon's developed some scratches," said Rep. Tony Coelho (D-Calif.) of President Reagan's difficulties in the last month. "Things are sticking to it now, and once they start sticking, they build up."

And, if you were a Democrat at last night's 22nd annual Democratic Congressional Dinner, it was your responsibility to provide a steady supply of criticism to help the process along.

There were, however, different ways to do it. Some went with blunt.

"It's been a fiasco," said Sen. Howard Metzenbaum (D-Ohio) of Reagan's 10-day trip to Europe. "I'm sorry I'm sugar-coated," he added, smiling.

"Bitburg is behind us, but things have just not been falling the president's way."

Others added a little praise, but ended up in about the same place.

"He got nowhere as far as trade's concerned," said House Speaker Thomas P. (Tip) O'Neill Jr. (D-Mass.) of the trip. "The fact that they were rude to him in his speech this morning -- I thought he handled that very well. But all in all, the president hasn't had that good a month."

And some were tactful.

"I think we often expect too much of these summits," said Senate Minority Leader Robert Byrd (D-W.Va.)

The $1,000-a-plate dinner at the Washington Hilton raised $1.65 million for the Democratic Senate and House campaign committees. More than 30 senators, more than 100 representatives and a swarm of lobbyists attended.

It was the kind of event where every back seemed to have a hand patting it, every mouth a "How are you!" flooding from it. The lobbyists surrounded their chosen targets, everyone was so glad to see everyone else and the phrase "our polls show we're doing well" was as popular as a senior senator.

Invitations to these things might as well say "Black tie and big grin."

"I feel the Democrats are having a very successful dinner," said Rep. Steny Hoyer (D-Md.), who just happened to be on the dinner committee. "That means an awful lot of people don't feel the Democrats are down. I think the Democratic party is very vibrant."

1,900 vibrant people attended. Each of them seemed to have vowed to greet all 1,899 others.

"This is not a speech night," said Carter White House aide and political consultant Anne Wexler. "It's a tradition that no one makes long speeches. Everyone likes to walk around and visit."

All that visiting can be exhausting.

"This is the fourth time since Saturday I've been in black tie," said one political consultant who planned to duck out before dinner. "I want to eat at home."

But most of the guests managed to make it through the meal, their energy unflagging even when they weren't quite sure at whom it was directed.

"Oh, that's whatsherface from George Mitchell's office," said one woman. "What's her name?"

An instant later the two were embracing.