ALBANY – The Republican Party in New York could be facing a doomsday scenario in November if Thomas Golisano, the Rochester billionaire who is considering a run for governor, does not win the Republican nomination and runs on the Independence Party line, political analysts said.

If the Republicans nominate someone other than Mr. Golisano and that candidate flops in the general election, the GOP could end up being downgraded to third-party status, they said. Such an outcome would have a ruinous effect on party machinery and patronage and would threaten the party’s control of the Senate.

“I don’t think it’s far-fetched because if Spitzer runs a great campaign, he leaves not many voters,” a professor of political science at Syracuse University’s Maxwell School, Jeffrey Stonecash, said. “It could happen.”

The party for at least the next four years would fall two places on the ballot, to Row C, if Attorney General Eliot Spitzer or another Democratic candidate wins in November and Mr. Golisano runs on a third-party line and comes in second.

Republicans barely avoided such a catastrophe in 1990, when the Republican nominee, Pierre Rinfret, a little-known economist, outpolled Conservative candidate Herbert London by just 37,000 votes.

“It has to be on their minds because it almost happened in 1990,” a professor of political science at SUNY Cortland, Robert Spitzer, said. “It’s not just hypothetical.”

The prospect of being consigned to minor-party status could be a significant factor for Republican Party leaders as they wrestle with their decision of who to nominate for governor.

At the moment, Republican leaders insist they aren’t considering such a chain of events and are focusing on settling on the best candidate to match up against the Democratic front-runner, Mr. Spitzer, who will likely be challenged within his own party by Nassau County Executive Thomas Suozzi.

“That’s craziness,” the executive director of the state Republican committee, Ryan Moses, said. “You’re not Row C when you win the governor’s race. The bottom line is the Republican Party will field a very strong ticket that will lead to historic victories in 2006.”

Mr. Golisano, a co-founder of the Independence Party who changed his party registration to Republican late last year, has indicated that he will announce his political intentions by the end of the month, and his closest aides say he still has not made up his mind about running for governor for a fourth time. As a third-party candidate, Mr. Golisano won 14% of the vote in 2002, spending $75 million mostly of his own fortune. He received 8% of the vote in 1998 and 4% in 1994.

If he does decide to run, it’s far from clear that the Republicans would endorse him.

While the majority leader of the Senate, Joseph Bruno, has encouraged Mr. Golisano to run, the chairman of the Republican Party in New York, Stephen Minarik, has personally endorsed a former governor of Massachusetts, William Weld. County chairmen participating in an informal straw poll last month were divided between Mr. Weld and John Faso, a former minority leader of the Assembly. Some county leaders did not take part in the poll, an indication of support for Mr. Golisano, who is the owner of the Buffalo Sabres and the founder of Paychex, a payroll processing firm.

In order for the doomsday scenario to happen, Mr. Golisano would have to lose in a Republican primary – not an unlikely possibility, given that many of his social libertarian views aren’t shared by the Republican base and that he has spent the last three elections viciously attacking the Republican governor, George Pataki.

If he loses a primary vote, Mr. Golisano could go back to running as third-party candidate on the Independence Party line and spend millions more dollars to attack the Republican nominee. Both Mr. Weld and Mr. Faso are trailing Mr. Spitzer badly in the polls.

“You don’t win by winning,” a veteran political operative, who asked not to be identified, said. “It’s dangerous for them to primary him.”

If Republicans fall to Row C, the entire field of Republican candidates running for statewide and county would be moved to a less prominent position on the ballot, which put the contenders at a disadvantage because voters are less likely to vote for candidates who aren’t in the two prime rows.

With the two leading parties given the power to organize the election machinery, the party would stand to lose hundreds of patronage jobs, including all of the state and county board of election commissioner slots.

“It would mean that the Republican Party suffers a huge loss in prestige and patronage in every county in the state,” the SUNY Cortland professor, Mr. Spitzer, said. “It would be disastrous for them.”

The president and CEO of WAMC/Northeast Public Radio Albany and the publisher of the Legislative Gazette newspaper, Alan Chartock, said the party is facing a tough road ahead no matter who it nominates for governor.

“The Republican Party is in deep trouble,” he said. “I can’t see a single ray of hope for them in the coming elections. What they are doing right now is arguing about the deck chairs of the Titanic.”