Enjoying a midsummer spirit of victory in mid-March, Ronald Reagan has begun tendering offers to his one-time presidential opponents to help them pay off their campaign debts -- all in the name of Grand Old Party unity.

The proposal of Reagan and his advisers is for a series of "unity dinners" to raise funds to help pay the debts of the 1980 presidential campaigns, according to spokesman for two of the men who were once challenging Reagan, Sen. Howard H. Baker Jr. and John B. Connally.

Reagan's campaign manager, William Casey, said in a telephone interview that he has suggested to "some other candidates" that Reagan might appear at fund-raising dinners to help them retire their campaign debts, though no agreement has been reached.

"It is an idea to which we are attracted," Casey said. "But so far it has only been discussed. There are some legal problems and other problems."

One minor problem might be the fact that only about 17 percent of the delegates to the 1980 Republican National Convention have yet been chosen. Front-runner Reagan still has two opponents -- John B. Anderson and George Bush -- who insist that they have a shot at winning the presidential nomination.

At the Bush headquarters, top advisers were saying that they figured that talk of a Reagan nomination in mid-March is still premature, and that his plans to help the other candidates pay off their campaign debts would be better as a midsummer's nice dream.

"If Reagan is attempting to get the endorsements of Baker and Connally in this way, that's up to him," said Bush press secretary Peter Teeley. "But remember, in 1976, Ronald Reagan did not even win his first primary until March 25."

A spokesman for Baker and Casey had discussed the idea yesterday with the Baker campaign finance chairman, Ted Welch. "The idea is for some unity dinners to be held," the Baker spokesman said. "They would be to help Reagan raise what other money he could use and to help the other candidates do the same thing."

The Baker spokesman said that both Baker and his finance chairman are receptive to the idea.

In a related development, Rep. Phillip Crane said yesterday he is urging his supporters to work for Reagan's nomination, but stopped short of withdrawing from the race. He said he would make a decision on that by the end of the month.

He said he wanted his supporters to help Reagan in part "to make sure John Anderson doesn't get off the ground."

Reagan's offer to help his former opponents pay off their debts is an attempt on his part to unify the remaining factions of the GOP behind his candidacy.

A Connally endorsement of Reagan appears imminent.

Connally's close political associate, Ben Barnes, said last night that, "I feel confident that Gov. Connally will appear with Ronald Reagan next Tuesday" when Reagan is to campaign in Texas. Barnes added, "John Connally is the kind of guy who doesn't do anything half way -- whether its an endorsement or compiling a campaign debt."

When Reagan spokesman Charles Tyson was asked whether Connally had agreed to appear with Reagan in Texas Tuesday, Tyson replied, 'That is something I can neither confirm nor deny."

John B. Connally III, 33, son of the former Texas governor, said his father has talked with Reagan on several occasions since withdrawing from the campaign after being soundly defeated by Reagan in the March 8 South Carolina primary.

"There have been some preliminary discussions" about Reagan helping his former opponents to defray their campaign expenses, young Connally said. "Obviously, we are all looking for every way we can think of to raise money."

The Connally campaign debt will be well over $1 million he said. Baker's spokesman said his candidate's 1980 campaign debt is about $650,000.

According to young Connally, his father's campaign, which raised money lavishly from big business and spent it in even grander fashion, has a particular problem when it comes to paying off its campaign debt. Many of the Connally contributions had already donated their $1,000 limit set by federal law, he said.

"These people could not buy a ticket to another Connally dinner and contribute another $1,000 even if they wanted to," he said. "But they could contribute to a dinner that Reagan would run and that my father would appear at as part of a joint event.

"If you could handle it from an accounting standpoint sufficiently to satisfy the FCC [Federal Election Commission] it could be done. But these are very, very preliminary internal discussions that are going on among these candidates."

Young Connally, who worked actively in his father's campaign added, "I think it's a great idea."

The elder Connally, after talking with Reagan shortly after withdrawing from the race, also proved instrumental in making the Republican front-runner where he is today.

Former president Gerald R. Ford has been counting on Texas Gov. Bill Clements and Ohio Gov. James A. Rhodes to provide key support in delivering delegates from these crucial states if Ford decided to make the race.

But both Clements and Rhodes spoke with Connally and heard Connally's view that it would be difficult, if not impossible, for Ford to enter the race so late and still defeat Reagan. Clements and Rhodes then told Ford they had decided to remain neutral in the contest, and Ford called off his candidacy.

"My father was not being part of a stop-Ford movement," said the younger Connally. "But I think it was more a matter of his stating the hard realities. He said it would be a mistake [for Ford to run]."

He added: "Ronald Reagan is clearly going to be the Republican nominee. There's no question about it, and there's no reason to wait all the way to the convention to start paying off these debts."