Here is what is going to happen next Tuesday:

Walter Mondale is going to win. And not just in the District.

Or so insisted about 300 furiously enthusiastic Democrats at last night's "Countdown to Victory" party at the Capital Hilton.

The polls? Polls don't vote. He's going to win. They said it again and again. They waved their Mondale/Ferraro posters again and again, holding them backwards so the TV crews covering the evening could read their message.

"Let us not despair of what the polls show," said Mayor Marion Barry, the top organizer for the Mondale-Ferraro ticket in the District. "I'm one of those who don't rely on the polls. In 1978, I was supposed to come in third in the Democratic race for mayor according to the polls. But you see who is mayor, don't you?"

The District is probably the only jurisdiction in the country where Mondale is assured of winning Tuesday, but the optimistic parties were being held across the country. Mondale supporters, most of them paying $100 each, gathered in 25 cities to cheer and watch a TV satellite hook-up to Geraldine Ferraro in Philadelphia and Mondale in Chicago. The D.C. party was expected to raise $50,000, and the entire evening a total of $1 million, all of it to pay for a media blitz during the last six days of the campaign.

"I expect an unexpected win for Walter Mondale," said Mondale campaign national co-chair Charlene Drew Jarvis, as Mary Travers of Peter, Paul and Mary sang "Where Have All the Flowers Gone?"

"I think that even though an election is approaching, people don't really focus until the last week or few days," Jarvis said. "They will go in there thinking back to the issues that really matter."

The polls were almost as unpopular as President Reagan.

"Don't worry about the polls," said D.C. Del. Walter E. Fauntroy, who is campaigning for Mondale throughout the country. "I've witnessed the enthusiasm of the people."

From Philadelphia, Ferraro called out, "Let others say this election cannot be won. I say it can be. I say it will be. I say it must be."

From Chicago, comedian Robin Williams said, "Reagan -- they say he's a nice man, a nice man. If you want a nice man, why don't you elect Mr. Rogers?"

And in Washington they yelled some more.

That was the party line at the party. Every once in a while someone gave a smile a little more rueful than the rest, but even then, the word "lose" was avoided. Other phrases, like "not a landslide," sufficed.

"I don't think it's going to be the sweep some people think," said Sharon Pratt Dixon, the District's Democratic national committeewoman.

And Mary Travers, who has been singing for Mondale and congressional candidates around the country gave that smile and said, "I think it's going to be a lot closer than a lot of people think."

A win?

"One can hope."

And after bands in Philadelphia and Chicago had played "Happy Days Are Here Again," Philadelphia Mummers had strutted across the screen, Mondale appeared, courtesy of a huge satellite dish parked out on 16th Street.

"The American people, quietly, with dignity, make up their minds and move," he said. "I'm convinced that's happening now. It's time for new leadership. It's time to move on."

Segue to pictures of the candidates, Carly Simon singing the song she wrote for the Democratic National Convention, "Here Comes the Turn of the Tide." The cheers grew, the posters waved.

"I think after tonight, if there is any question in our minds, it should be erased," Barry then told the crowd. "There is no question that Fritz Mondale and Geraldine Ferraro will win on November 6."

And the crowd rolled up the posters and left.