Daniel Patrick Moynihan, who knows more things about more things than anyone else in the U.S. Senate, and conveys this occasionally with the engaging bashfulness of a sideshow barker, was momentarily stumped.

For days, he had lectured associates and voters about all manner of things from the history of America's waterways and gothic church architecture to theories on socioeconomics and nuclear weaponry. All this while floating at his leisure down the Erie Canal, campaigning the way they did in the good old days, from the enviable position of a politician who has a lock on his reelection.

But when asked whom he voted for in the 1980 presidential primary -- President Carter or Sen. Edward M. Kennedy -- he suddenly was all flannel mouth and flummery: "Uh, uh, I guess I voted for Carter. No, you better not write that down. Because I can't really remember. I know I voted absentee. . . . Uh, Carter or Kennedy? I'm not sure. . . . I guess it was Carter. . . . Yes, I'm sure that's what I did. Carter. Seems to me you can't go and tear down the president of your own party. So I voted for Carter!"

This will be news to his constituents, who will remember only that Moynihan successfully evaded all entreaties to declare his favors. "It was crucial that Pat stay neutral in 1980 and not antagonize any of the activists in the party," said Moynihan's campaign manager, Timothy Russert.

Success brings with it its own moments of truth, and Moynihan, the neo-conservative/ neo-liberal Democrat, had only nominal opposition for renomination in the New York primary yesterday with his reelection in November all but assured.

The former champion of the conservative wing of the Democratic Party in Congress will be the candidate of both the Democrats and the Liberal Party in New York on Nov. 2, avoiding a once-feared threat that he might lose votes of left-leaning Democrats to a Liberal nominee. His polls are telling him that his approval rating is 65 to 69 percent, while his Republican and Conservative opponents are still struggling to get into double figures.

He has been the beneficiary of a little good fortune and a lot of good strategy.

The National Conservative Political Action Committee helped make Pat Moynihan what he is today. They did it by targeting him for defeat -- and then pumping big money into New York to get the job done.

What NCPAC accomplished, mainly, was to set the liberals' chablis to boiling. So much so that, before they were done, the Liberal Party agreed to do something its members had once vowed never to do again: endorse Moynihan.

Moynihan had been President Nixon's top White House adviser on domestic affairs and won conservative plaudits with his stands for increased defense spending, anti-Sovietism and getting tough with the Third World.

Moynihan also introduced a bill to provide tuition tax credits for students of private and parochial schools and, according to Liberal Party vice chairman Raymond Harding, Moynihan had "made a commitment to us that, if elected, he would do nothing to use federal funds to aid private schools. But then, lo and behold, the next year he introduced his bill . . . . It was a breach of a commitment."

Moynihan contends that he and Liberal Party officials had never talked about funds, let alone made a commitment.

Russert then began the painstaking work of trying to build bridges, heal wounds, win friends and discourage liberals from challenging Moynihan in a Democratic primary. He worked to get the Liberal Party and the state's senior senator talking again.

"Our dialogue with Moynihan was reinstated because of the work of Tim Russert," Harding said. "He showed us an attitude that had changed . . . and then NCPAC came into New York."

NCPAC's attack featured radio ads proclaiming that Moynihan was "the most liberal United States senator in 1980," even more liberal, it said, than Kennedy of Massachusetts. Russert turned the attack to Moynihan's benefit, enlisting Rep. Morris K. Udall (D-Ariz.) and former senator Frank Church (D-Idaho) to send letters to all liberal New York contributors, including transcripts of the NCPAC ad. Their message: a man should be known by the enemies he makes.

"When NCPAC came in, it became inevitable that we were going to endorse Moynihan," said the Liberal Party's Harding. "We just did not want NCPAC to succeed in New York."

While getting the Liberal endorsement was made possible partly by the conservative zealots, ridding Moynihan of tough opposition in November by Republican congressman Bruce Caputo was made possible entirely by Bruce Caputo.

Once a moderate Republican, Caputo emerged early as heir apparent to the GOP Senate nomination and began moving to the right. Russert began tracking Caputo's record and utterances for inconsistences.

Thus, last December Russert noticed inconsistencies in the way Caputo described his military service record, as "a former draftee" in public comments, and as an Army second lieutenant in Who's Who, while his biography in the Congressional Quarterly stated, "Military Record: None."

When a check of Army computers turned up no record of Caputo's military service, Moynihan and his advisers opted to get Caputo out of the race quickly, rather than saving it for an October surprise that would smack of politics. And to do it, if possible, without leaving fingerprints.

Caputo obliged. During lunch with two reporters, he talked about his military service, and for good measure called Moynihan a buffoon. The reporters called Russert for reaction and the deed was done in news stories throughout the state.

"All it really took was for a journalist to say to Caputo, 'What date did you enter the service and what date were you discharged?' " Russert says. "And -- boom! -- it was over.

Moynihan has marshaled his case. He has heard the liberals who long ago said he traded in his liberal credentials when he joined the Nixon White House and that he hasn't been the same since. More recently, neo-conservative Democrats who once called him a leader have said privately that he has gone back to his liberal ways.

Moynihan responded that he has stayed very much the same in a career that has taken him through the Kennedy and Johnson subcabinets, Eastern academia, the Nixon White House, ambassadorships to India and the United Nations, and the U.S. Senate.

He has assembled a few documents in his behalf. "There is me on crime," he said, reaching for a 1965 speech text he has culled from his files in preparation for this interview, "saying if we are going to be part of this successful liberal tradition we must deal with this.

" . . . We also went through this neo-conservative thing. I don't apologize to anyone for that . . . . I was involved with most of those issues before they were fashionable . . . "

But the so-called neo-conservatives come down rather harshly on the Moynihan now. "What he's doing on the nuclear issue really ticks me off," said one who is outraged that Moynihan has endorsed several different nuclear freeze proposals, one of which would first increase the number of nuclear weapons. "He goes on television and says we don't need all those nuclear weapons just to 'make the rubble bounce.' Well, Professor Moynihan would have called that 'Demogoguery!' and said that the issue is deterrence."

How could he endorse all these freeze proposals? "Very assertively!" Moynihan replied, blossoming into full rhetorical flower. "The temptation is to divide us -- bang! -- but we have to keep our eye on the end result. We keep going up, and we have to go down. Whether you stay the same and go down, or build up to go down is just a matter for negotiation."

In the Senate cloakrooms, Moynihan is viewed with both amusement and admiration by his colleagues. They respect the job he has done as vice chairman of the intelligence committee, for example, but he is known more for his oratory and conceptualizing than for his leadership within.

They say he sees the Senate as a bully pulpit, both on the Senate floor and in the semi-privacy of the Democratic caucuses. One source recalled the time Moynihan took the floor during a closed meeting of Democrats trying to work out strategy and tactics on the upcoming budget and tax fights, and began to lecture on the theories of economics.

Moynihan told an interviewer that "of my Senate class, there is only one person -- Dennis DeConcini (D-Ariz.) -- who has enacted more bills than I." Then he added, "I know an awful lot about the American government."

Urged by followers, many of them people of influence, to run for president, Moynihan has insisted he will not run.

"You have to really want it to start so early and run so hard," he said. "It proves to be all-absorbing, and in the end heartbreaking, for most people who have run."

Would he run as vice president, if asked by a presidential nominee?

"Oh sure," said Moynihan, erupting in cheer. "That's a different enterprise altogether."