They called yesterday "the first day of the Reagan Revolution." They proclaimed "the return of the Democratic Party." And they celebrated the ironies and the promise with wine, songs like "Put On a Happy Face" and pep talks. Last night 1,000 Democrats gathered, celebrating the addition of $950,000 to their depleted coffers and celebrating their own new beginning on the day they thought the Reagan economics would start to backfire.

"Today is D-Day, Oct. 1. Their program has begun," Speaker of the House Tip O'Neill said last night at the Democratic National Committee's $1,000-a-plate dinner. "Beginning today Ronald Reagan and David Stockman have no excuses. Tonight I am proposing a new timetable for the success or failure of the Reagan program: Nov. 2, 1982."

The audience of party stalwarts, Carter administration veterans and a good portion of the Democratic House and Senate echoed the partisan energy. "Today, the new birthday of the new administration, people can see the reality," said Glenn Watts, president of the Communications Workers of America. "I lived through the Depression, but I was never frightened like this before. Now I am feeling better. Three months ago they wanted to coronate the man, now they want to string him up. I'm feeling better." Observed Rep. Morris Udall (D-Ariz.), "the mail is beginning to build up. In another 60 days everyone will see they are paying a heavy price."

Ironically, as the economic policies chipped away at the urban programs, the dinner saluted the Democratic mayors. "Our mayors will bear the brunt of much of this new beginning," said Senate Minority Leader Robert Byrd ( James McGee of Dayton, Ohio, had one strong word for the effects of the Reagan programs: "Catastrophic." Henry Maier of Milwaukee, the dean of American mayors, predicted the social services cuts will destabilize the cities. "These policies will not decrease the social unrest in our cities; they will increase it.What have we gained if we trade federal red ink for blood in the streets -- either in the form of crime or riot."

Last night public "presidential '84" speculation was scarce. Sen. John Glenn (D-Ohio), mentioned as a possibility in 1984, laughed, "It's way too early to line people up. I know that's the favorite Washington game." But if applause and standing ovations are any measure, a lineup of Walter Mondale and Averell Harriman would suit last night's celebrants.