At the Shoreham the Republicans had roast beef. At the Capital Hilton the Democrats had none -- well, they had hopes for a state or even two. The Republican parties were so crowded that you couldn't see your feet. At the Democratic parties, that's all they seemed to be looking at.

From Richard Viguerie's house, where the menu was quails' eggs, to Pamela Harriman's, where it was crow, from hopes that kindled to dreams that dwindled, the Washington party scene last night was a microcosm of the passions that drive us through these first Tuesdays of Novembers. Herewith, a sampling.

At 7 o'clock, with the Shoreham ballroom swaying and the bands playing, you could see the projections -- Mississippi! New Hampshire! -- on the four large television screens across the ballroom.

By 8 o'clock -- Ohio! North Carolina! -- you couldn't see your feet or hear yourself think as 10,000 Republicans added fervor to astonishment while the night wore on -- Pennsylvania! New York! -- and hardly anybody seemed to mind that the bar was cash and the food was potato chips, peanuts and little pastry goldfish.

"I think I'm in a political twilight zone," said Sen. Paul Laxalt (R-Nev.), the man often described as President Reagan's best friend in Congress and the chairman of his reelection campaign. "I knew it was good, but nothing like what's happening."

"The president," proclaimed Ambassador William Middendorf, "now has a mandate to save the country."

And by the time deputy campaign manager Lee Atwater hoarsely called out Reagan had won, the crowd was uncontrollable, bellowing like fans of the winning football team every time a Democrat took a dive. "I just saw Ken Duberstein and he says the House looks wonnderfulll," said Ken Crib, assistant to the counsel to the president. "I hear there's an overall 51-49 generic Republican vote. Never in my lifetime."

Cubans for Reagan! Scandinavians for Reagan! Youth for Reagan!

About half the people in the ballroom appeared to be under 35.

Stephen Edelin, 24, the president of Students for a Better America, had grown up Democratic but switched to the Republicans in 1980 after he worked in a campaign for Rep. Timothy Wirth (D-Colo.). "I was disillusioned with the liberal agenda. The president has a mandate to continue to improve the health of the economy. Now the young people are so much a part of his support because we all feel that our generation has soundly rejected all the New Deal philosophy."

They partied in lobbies, in rooms, in hallways. The elevators were so hopelessly jammed that lights as bright as former secretary of the interior James Watt and Ambassador to the United Nations Jeane Kirkpatrick were taking the stairs, which were merely packed.

In a fifth-floor smoky control room a dozen aides watched three televisions and talked on 10 phones monitoring state-by-state results.

At 10:25, a Cabinet officer parade including Secretary of Transportation Elizabeth Dole, Secretary of Commerce Malcolm Baldrige, CIA Director William Casey and Secretary of State George Shultz marched on stage to massive cheers, and marched off to the tune of Michael Jackson's "Billy Jean."

The best place to watch the results was at a party hosted by Richard Allen, former national security adviser to the president. Allen, now head of a group called International Republican Cooperation Fund, and his party took over half the hotel lobby and adjoining function rooms. Ambassadors and campaign officials ate roast beef and ice cream sundaes and actually got to see the televised coverage in near sane surroundings.

If there was ever a mixed bag of election night emotions it was here with supporters celebrating their long-expected win while reflecting on the poignant reality that this is the beginning of the end of the Reagan era.

"It's quite nostalgic," said Roger Stone, a Reagan-Bush Northeast coordinator, who, at 32 years old, can say he has been a decade-long Reagan crusader. "I had the opportunity to sit with the president on Air Force One the other day and I said 'Mr. President, I worked for you for six years and through three campaigns and this was the best of all.' I've got to tell you I feel sad. There'll never be another Reagan campaign."

On the other hand, trust Lyn Nofziger to put a different spin on the ball.

Nofziger, a consultant to the Reagan-Bush campaign who was introduced as "the living legend of American politics -- the one who has been with Reagan the longest," told the crowd: "I've been with the president since 1966 and this is my last one and I am glad it is over. The politics of running a campaign is a young man's job."

The ball got still a different spin from Richard Allen. "Baloney," Allen said, when asked if tonight's win means an end to the Reagan campaigning era. "He will campaign for the next 20 years. Don't think he will retire and just cut brush on the ranch."

As the victory mounted, some of the crowd brandished hand fans with Mondale's picture on them in a downcast pose.

About 10 minutes before the long-anticipated speech by the night's victor began, Atwater for the last time announced a roll call of states in the Republican column. Montana! Iowa! Utah! By now the massive map in the ballroom was almost totally Republican.

When the faces of Ronald and Nancy Reagan filled the four giant screens and several small television sets, only 500 of the true blue supporters were left. Some were hanging on to one another, others had taken their shoes off and a few were scavengging for souvenirs and campaign buttons. But when Reagan spoke, they were reenergized. Every time the crowd in the Los Angeles room shouted, the ones at the Shoreham responded. And then a thunderous roar went up as the President touched on the night's spirit by saying: "Tonight is the end of nothing. It is the beginning of everything."