WASHINGTON – A billionaire businessman who failed to beat Governor Pataki three times on the Independence Party line, Thomas Golisano, will switch his party affiliation to Republican today in an effort to gain major party support in another run for governor next year, a top New York State Republican official said yesterday.

The source, who asked not to be identified because of the delicacy of discussions surrounding next year’s race, said that top state Republicans have warmed to Mr. Golisano out of concerns about a Democratic romp in the 2006 elections. In three straight gubernatorial runs, Mr. Golisano has launched withering attacks against Mr. Pataki.

“He wants to be on the Republican ticket,” the source said. “He knows it holds more value being with the larger party, and the Independence Party already said it will back him. He’s got name recognition, he owns successful businesses in an economically depressed part of the state, and the governor’s a lame duck. What does he have to lose?”

With Senator Clinton and the presumptive Democratic nominee, the state’s attorney general, Eliot Spitzer, leading their party’s ticket next November, Senate Republicans find themselves in danger of losing their hold on a tenuous 35-27 majority in the state Senate for the first time in decades. Fearing a Democratic rout, the Senate’s majority leader, Joseph Bruno, of Rensselaer, is said to have pinned his hopes on Mr. Golisano.

Mr. Bruno had breakfast with Mr. Golisano at the Desmond Hotel in Albany two weeks ago to discuss the 63-year-old businessman’s interest in another run, an aide to Mr. Bruno said. The meeting took place shortly after Mr. Bruno spent an afternoon with a former governor of Massachusetts, William Weld, discussing his gubernatorial ambitions. Aides to Mr. Bruno say he does not have a favorite and is wary of a primary fight.

“He’s not concerned about his seats. He’s not concerned about his majority. And his full conference is behind him as a leader,” Mr. Bruno’s spokeswoman, Lisa Black, said. “But the senator is exploring all of the gubernatorial options.”

A number of state Republicans have complained over the past year that Mr. Pataki, who announced in July that he will not seek another term, is leaving the party without a strong bench of candidates for statewide office. Aside from the governor, only one Republican, a former attorney general, Dennis Vacco, has won statewide office in the past 12 years. Polls suggest the party is now poised to lose the governor’s office too.

A Quinnipiac poll from Tuesday showed Senator Clinton and Mr. Spitzer maintaining strong leads over a number of potential Republican opponents. The same poll reported that Mr. Golisano, who spent $75 million of his own money in earning only 14% of the vote three years ago, is now the no. 1choice among Republican voters. He polled ahead of Mr. Weld and a former state assemblyman, John Faso, with 33% of party voters saying they would choose him against Mr. Spitzer. The secretary of state, Randy Daniels, is also considering a run for governor.

Republican Party officials are publicly supportive of a party switch by Mr. Golisano.

“We encourage all people to become members of the party,” the executive director of the Republican State Committee, Ryan Moses, said. “We want people in the Republican Party. As far as him running as a candidate, it’s speculation really. You’d have to ask Tom Golisano if he’s running for governor.”

But political insiders say party leaders fear Mr. Golisano’s entrance into the race because it would almost assure a primary fight that they are hoping to avoid. With registered Democrats outnumbering Republicans five to three in New York, the party is at a major disadvantage in any statewide race. Its chances narrow even more, some argue, when candidates are forced to spend money and energy fighting one another.

Mr. Golisano has few fans among party leaders after hammering its candidates in three elections. But because he could potentially buy off county leaders by offering to pour money into Senate races, political insiders are divided on whether the state Republican chairman, Stephen Minarik, would consider supporting him as a nominee. Mr. Minarik is openly supportive of Mr. Weld and is an appointee and close friend of Mr. Pataki.

“We can’t ignore the fact that he’s there,” the Republican chairman of Rockland County and one of eight vice chairmen on the state committee, Vincent Reda, said. “We have to invite him to the table at some point, and I’m sure Chairman Minarik would go along with that.”

Party officials have been watching Mr. Golisano closely for weeks. Potential candidates who are not Republicans have until October 14 to switch affiliation and still qualify for a potential primary next year without first getting permission from party leaders. Even if Mr. Golisano does switch, as expected, the state’s 62 county chairmen, who have been weighing other candidates for months, will need convincing to back him.

“I don’t see a whole lot of enthusiasm for him from the people I know,”the Republican chairman of Orleans County, Dan Olson, said. “I kind of don’t think that he would get the support of people I know. I don’t know of anybody who’s been talking to him but Joe Bruno. I kind of like John Faso myself.”

Mr. Golisano, 63, is the founder of Paychex, a Rochester-based company that handles payroll for small businesses. He also owns the Buffalo Sabres hockey team. Senate sources said Mr. Bruno, a former businessman, likes Mr. Golisano because he is an entrepreneurial success in an economically depressed region of the state. Others say Mr. Golisano is too independent to be trusted with a leading role in an already-delicate party.

“He’s poised to lead a hostile takeover of the Republican Party, and that will do serious damage to the party, to George Pataki, and to everyone else down the line who wants to run as a Republican,” a top state Republican said on condition of anonymity.

Mr. Golisano did not return a message left at his business late last night.