George Bush brought his presidential campaign back to Yale today, with a barbed attack on his rivals, some comic advice on the perils of being a "preppy" in politics, and a promise to stay in the fight until convention time, no matter what happens in Tuesday's Connecticut primary.

Returning to the campus where he is remembered as a smashing success -- the Phi Beta Kappa captain of a championship baseball team -- Bush said that, despite the battering he has taken in seven of the first nine primaries from Ronald Reagan, "I am in this race to stay. I will be in this race in July -- at the Republican convention in Detroit, and then in the fall."

During a feisty question-and-answer session at the Yale Political Union, Bush tangled repeatedly with students backing Rep. John B. Anderson. Bush's Connecticut managers believe that Anderson may cost Bush a desperately needed victory in the state where he was raised and which his father, Prescott Bush, represented in the Senate.

When one Anderson supporter accused him of distorting Anderson's positions, Bush flared back that "for months, I let that character sit around and call me a Ronald Reagan in a J. Press suit . . . I've got real differences with him. I oppose a 50-cent gas tax. I don't think you can cut the defense budget. I don't think it's wrong to shoot for a balanced budget. And I will support the nominee of the Republican convention, instead of sanctimoniously holding myself above the party."

In the aggressive tone he has maintained throughout a grueling six-day campaign for victory in Connecticut, Bush also laid into President Carter for running "an incompetent administration unequal to the task of providing the kind of leadership this country needs."

"Since taking office," he said, "Jimmy Carter has . . . found occasion to fault a Congress controlled by his own party; the legal profession; the medical profession; telephone connections between the State Department in Washington and the American mission to the U.N.; and last but not least, a mythical beast -- spawned, I believe in the swamplands of south Georgia -- called 'national malaise.'"

"Symbolism and scapegoatism . . . are not a substitute for governing," Bush declared. "They are merely evidence of a weak presidency."

Bush won laughter and cheers from the Yale students by offering his "rules for political survival" to those who might be thinking of their own campaigns. "Being a Yale graduate," he said, "has certain political disadvantages."

"Remember that William Loeb [the publisher of the Manchester Union Leader, which blistered Bush in New Hampshire] doesn't like what he calls 'clean fingernail Republicans,'" Bush said. "Arrange to give your car personal lube job before crossing the Manchester city limits.

"Never use the word 'momentum' until the last vote is counted in the last primary.

"And never let your opponent pay for the microphone in a political debate."

Bush flies to Wisconsin Tuesday to begin campaigning for the April 1 primary there. But his aides acknowledge that, without a home-state victory over Reagan in Connecticut, his chances of reviving his campaign would be minimal.

Meanwhile, Reagan, the Republican front-runner, carried his campaign into New York state, where he received commitments of support from five delegates who had previously been running on an uncommitted slate.

Among those coming out for him today were state Sens. James Donovan of Utica and Fred Eckert of Rochester.

Reagan is expected to make a strong showing in the New York primary, not only among the delegates he has fielded, but also among those running uncommitted but who are now scrambling to catch the Reagan bandwagon before it rolls on out of the state.

At a news conference in Syracuse, N.Y., Reagan had a little trouble hearing a questioner who asked him about the situation in Indonesia. Reagan gave an answer that dealt with Indochina. With the fall of Vietnam, Reagan said, the "domino theory" saw the fall of Laos and Cambodia, and there is still a threat to Thailand. He added: "We have something of a responsibility because we did walk out on an ally."

Reagan also said that he did not think that the shah's decision to take up residence in Egypt will be a threat to the American hostages in Iran. And he added that the United States is making a big mistake by acceding to the Iranians who hold the hostages and "their salami theory," which he explained was their effort to slice off one more pre-condition every time the Carter administration yields to the last pre-condition.

Reagan said the United States made a mistake by not making it clear in "the first days" that it was prepared to do "something" -- he never explained just what -- if the hostages were not returned.

He said that as of now, "Unless our government reverses course very suddenly, we have endangered Americans all over the world" by not taking a firmer stand in Iran.

And talking like a candidate who feels he has the nomination won, he even had a charitable word for the press coverage of his campaign.

He said in answer to a question at a meeting of New York state editors, that when he first came east to campaign in 1976 and took a bus tour through New Hampshire, he and the "eastern press . . . sniffed each other like a couple of strange dogs."

Reagan recalled: "I knew I was that Neanderthal [in the minds of the press] and I could ever feel my horns grow as I crossed the Mississippi River." But he said that he thinks that he has been treated fairly and has even made some "treasured" friendships among reporters of the East. "They've even stopped asking me how old I am," he said.