From the Democratic Party's point of view, the significance of yesterday's defeat on the budget resolution in the House of Representatives was stark and simple. In the first test of strength with President Reagan and the resurgent Republicans, in the only part of the national government the Democrats still control, the Democratic coalition shattered.

On the key roll call, substituting the Reagan-endorsed budget for the one drafted by the Democrats on the House Budget Committee, 63 Democrats defected to give Reagan his 77-vote victory.

The basic facts are striking. The defeated Democratic alternative was carefully crafted by the new Budget Committee chairman, Rep. James R. Jones (D-Okla.), one of the most highly regared of the party's younger leaders. It was skillfully enough balanced to win initial support from all but one of the Democrats on Jones' committee. It had the full backing of the party's House leadership and of what purported to be a powerful coalition of labor and liberal interest groups. But when Reagan & Co. went to work, they rolled the Democrats with surprising ease.

The result, interviews with Democratic leaders and rank-and-file members indicate, is likely to be heightened criticism of the Democratic leadership, greater recriminations between liberal and conservative wings of the party and a fraying of political ties between elected Democrats and the interest groups that have supported them.

While some House Democrats profess to believe this was a one-time loss that could be reversed when the tax-cut portions of the Reagan economic plan come to a vote -- or even when specific budget reductions reach the floor -- more appear to believe that Reagan will remain in the ascendancy unless and until his economic policies are proved a failure in the real world.

Meanwhile, the Democrats are resigned to limping along fragmented, frustrated and -- in many cases -- politically frightened.

Rep. Leon E. Panetta (D-Calif.), a Budget Committee member, was telling a story in the cloakroom that seemed to epitomize the mood. He was visited a couple days before the vote by Ed Roberts, the California director of rehabilitation, seeking to save funds for his programs. "His arms and legs are paralyzed," Panetta said, "and he gets around in a motorized wheelchair, carrying a portable iron lung with him to assist his breathing.

"I was sympathizing with him, while trying to explain how frustrating it was in this atmosphere to try to save the kind of programs he was running. But he stopped me cold. He said, 'You don't have to explain. I've seen a lot of congressmen that are more paralyzed than I am.'"

How the Democrats got paralyzed and then pulverized on the budget issue has been a matter of unending and agonized discussion in the cloakroom.The starting point for everyone is Reagan's popularity, and his effective exploitation of that popularity in selling the program to the public and to individual members of Congress.

"He's a winner and he's a hero," said House Majority Whip Thomas S. Foley (D-Wash.), "and the American people like both. The feeling is that his program deserves a chance." Ray Denison, chief lobbyist for the AFL-CIO, which led the efforts against Reagan's budget cuts, said of the congressmen: "It's almost a metaphysical thing that's gripped these people -- a feeling they should do something even if it's wrong."

Nonetheless, there is an abundance of rank-and-file criticism of the leadership performance on this test. Questions have been raised about why the first full discussion of the Jones budget was not held in the Democratic caucus until three days ago, long after Reagan had nailed down the Democratic defectors. "The truth of the matter is that [House Speaker Thomas P.] Tip [O'Neill] and our guys got outworked and outhustled on this one," said a senior Democrat normally supportive of the Speaker.

That charge is resented by the leaders. "We can't offer favors or threaten people," Foley said. "That day is past. And, without trying to alibi for the leadership, I will just say I don't know of any plan that would have got Charley Stenholm and Charley Rangel together." Stenholm is a Texas Democrat who is one of the leaders of the new conservative caucus and Rengel is a Harlem Democrat with one of the most liberal voting records in the House.

There was no concealing the bitterness between the two wings of the party as the final vote neared. Liberals complained about the refusal of the leadership to offer them even a roll-call vote on which to record their opposition to a big increase in defense spending, and were further humiliated when their own amendments to shift money from defense to social programs drew only 69 and 119 votes.

A member of the leadership said scathingly, "The liberals have been asking for this. Reagan is the product of a decade of growing concern about the cost and efficiency of a lot of programs and regulations and about the neglect of the military balance in the world. The Democratic Party has given greater weight to the liberal wing than its numbers deserved and groups that held the party's conscience -- women and minorities -- have vetoed rational moves to addjust our policy. Well, that veto is over."

But among the liberal and minority Democrats, bitterness overflowed. "The old southern Democrat-Republican coalition is back," said Rep. Parren J. Mitchell (D-Md.). "You've got the same kind of split in the Democratic Party that blocked civil rights legislation for so many years. But this time, we who are liberals are not going to pull the Democrats' chestnuts out of the fire. You'll see liberals pulling away from the Democratic leadership. I don't know what our alternatives are, but it's not enough for us to play conscience of the party and always lose."

Rep. G.V. (Sonny) Montgomery (D-Miss.z), one of the leaders of the breakaway southern Democrats, discounted talk of a long-term split, saying, "I would hope things would settle down. We conservative Democrats want to stay under the umbrella."

But Montgomery's advice to his party is to "give the president his program." While O'Neil and others forecast a more disciplined Democratic vote on the upcoming tax-cut bill, Montgomery said the southern Democrats are hoping the president will be flexible enough to endorse a compromise bipartisan bill that would enable them to vote with Reagan once again.

Rep. Albert Gore Jr. (D-Tenn.), a moderate, said the budget vote was "the first tangible evidence of the serious disarray in the Democratic Party," but warned that there would be more such instances until the party and its allied interest groups build their grass-roots strength.

Voicing a judgment echoed by many other Democrats, Gore said the promised campaign by liberal and labor organizations on behalf of the threatened programs "just never happened. A lot of people took a dive on this vote because all the pressure came from one direction," he said.

The only consolation many Democrats could find in the situation was the belief that Reagan's economic policy will backfire on him. "We may have lost the battle, but we'll be better off in the long run," said Norman D. Dicks (D-Wash.), an Appropriations Committee moderate. "Now the Republicans take the responsibility for what happens to prices, interest rates, jobs and housing starts. I think in six months, we can show people we offered a very conservative, cautious, constructive program, and that Reagan's was the radical alternative."

In the same vein, Rep. Morris K. Udall (D-Ariz.) said, "I think a year from now, when it's obvious the medicine isn't working, interest rates are up, the economy is sluggish and energy prices are raised again, Reagan will be about where [Jimmy] Carter was."

Waiting for calamity is about the best the Democrats can find to cheer themselves these days.