Ronald Reagan's campaign chairman yesterday predicted that the race for the 1980 Republican presidential nomination will boil down to a contest between Reagan and John Connally.

Sen. Paul Laxalt (R-Nev.) said Connally is "coming on like gangbusters" in appearances around the country and he sees the former Texas governor as Reagan's most formidable competition for the nomination.

Connally, a Democrat until 1973, "is striking the chord" with Republicans and "the business community is flocking" to him.

Among the Republican challengers only Reagan and Connally, he said, currently have the ability to generate the kind of financial and organizational support to stay in the race "for the long haul."

"You can't minimize how important it is to be well financed and well organized," Laxalt added during a breakfast meeting with reporters.

In a lengthy discourse about Connally, the Reagan chairman only once raised any criticism of him, saying that the ultimate long-term question about the Texan is his "credibility problem." That was a thinly veiled reference to his switching of parties and his acquittal on charges of accepting a $10,000 bribe while he served in the Nixon administration.

The principal issue in 1980 "is going to be one of leadership," he said. "John Connally, in his appearance the last few weeks, is striking a responsive chord on this issue."

He is "apparently saying the right things, and he's saying them well," said Laxalt.

On other matters, Laxalt said:

Sen. Howard Baker Jr. (R-Tenn.) should resign his post as Senate minority leader if he formally announces his candidacy for the GOP nomination.

He expects Regan's performance to dispel widespread doubts about his age as the campaign progresses. Reagan is 68.

It is possible for a Reagan candidacy to survive early primary defeats in New Hampshire and Florida "but I think it would be tough as hell."