ALBANY – Governor Pataki’s decision to avoid what had promised to be the most challenging race in his long and unlikely career of political triumphs, announced with fanfare yesterday, sets the stage for a possible national run by the three-term Republican governor and leaves the party he energized in three statewide victories searching for someone to give it new life.

The long-awaited decision marks the end of an era that began with enthusiasm but saw that early excitement tempered by the realities of political compromise and the awful human toll and painful economic losses of the September 11, 2001, attacks.

It also marks a new beginning for Republicans in New York. By stepping aside, Mr. Pataki blew a whistle to start the race to find a candidate for governor next year.

That campaign may be made more difficult by the relatively narrow 16-month window Republican leaders now have to vet contenders, select a nominee, and raise the money needed to mount a serious challenge against next year’s presumptive Democratic nominee, Eliot Spitzer, the state’s attorney general.

Some observers said Mr. Spitzer’s double-digit lead over Mr. Pataki in statewide polls sealed the governor’s fate. Others said Mr. Pataki’s decision frees him to pursue a larger stage.

“He was going to have a very difficult re-election,” a veteran political pollster, John Zogby, said. “Nothing is impossible. But that’s not what you need, especially if you are going for a fourth term. Whether he makes good on the presidential ambitions or not, he was facing a very difficult race and the odds were against him.”

Mr. Pataki, 60, has already stated his interest in the 2008 presidential race despite a widely held view that his liberal stance on social issues makes him a long shot for the Republican nomination. He told reporters in Albany this spring that he wants to play a role in the next presidential race and traveled to Iowa, the site of the first presidential caucuses, earlier this month in a clear attempt to test the presidential waters.

One of the governor’s aides confirmed yesterday that Mr. Pataki told a half-dozen of his closest associates upon returning from Iowa that he would not seek a record fourth term. Mr. Pataki informed a wider circle of his decision during a dinner at the Executive Mansion Tuesday. Mr. Pataki also held a dinner for donors at the Water Club in Manhattan last night. Aides characterized the event as an opportunity to thank supporters rather than a national fund-raising launch.

Mr. Pataki gave no sign yesterday of his future ambitions, except to say he will “follow a new path, find new challenges,” upon completing his term. He chose instead to highlight the accomplishments of his tenure. Lawmakers will make that last pledge difficult for the governor to fulfill, given his new status as a lame duck.

The elaborate staging of the governor’s announcement -hundreds of state employees were asked to line a hallway through which Mr. Pataki walked, past a giant television screen broadcasting patriotic images and toward an elevated rostrum – suggested long preparation. Mr. Pataki’s wife, Libby, their four children, and his mother, Margaret, attended. An aide said the event, at which employees were prompted to applaud, was a week in the making.

Mr. Pataki did not take questions after the speech, but many of his political allies who attended did. In a sign that possible Republican contenders are already lining up for a chance to take on Mr. Spitzer, the governor’s associates began to drop names even before the crowd had dispersed. The names that surfaced seemed to reflect an emerging strategy by which state Republicans will draw on past successes rather than gamble on a new face, as they did with Mr. Pataki, who was a freshman senator when he scored an upset victory over another three-term governor, Mario Cuomo.

“Right now Governor Pataki would be the strongest candidate to run against any Democratic candidate that would run for governor,” the chairman of the state’s Conservative Party and a crucial longtime Pataki ally, Michael Long, said. “I don’t have a favorite yet, but there’s the possibility of John Faso, Rick Lazio, or Randy Daniels. And that’s just a start. I think you’ll see a lot more people get into the mix.”

Mr. Long said he is pleased with the governor’s timing but disappointed with the decision. He said Mr. Pataki had the best chance of any Republican at beating Mr. Spitzer, even as he lists other possible opponents. Mr. Faso is a former assemblyman who narrowly lost a race for state comptroller three years ago; Mr. Lazio is a former Long Island congressman who lost big but mobilized donors in a Senate race against Hillary Rodham Clinton in 2000, and Mr. Daniels is New York’s secretary of state.

Other potential candidates whose names have surfaced include a Putnam County assemblyman who has taken a lead role in attacking Mr. Spitzer at Republican functions, Patrick Manning; a state senator from Nassau County, Michael Balboni, and the district attorney of Westchester County, Jeanine Pirro, though most have said recently they expect Mrs. Pirro to run for attorney general. A congressman from upstate Saratoga County, John Sweeney; an upstate industrialist, Thomas Golisano, and a former Massachusetts governor, William Weld, have also been mentioned for the race.

Republicans put a good face on Mr. Pataki’s decision, denying he will be hampered by lame-duck status in the coming year or that the party is unlikely to find a strong replacement for him. But political observers agreed the governor leaves his party weaker than it was when he took office. They predicted difficult times ahead for a party that has won three consecutive statewide governor’s elections despite being outnumbered by registered Democrats 5-3.

“It’s generally true that parties tend to become dependent on incumbent governors,” the dean of the College of Arts and Sciences at the State University of New York at New Paltz, Gerald Benjamin, said. “They come to depend on the incumbent for fundraising and resources and, absent the governor, the party has a hard time organizing and directing its energy.”

Mr. Pataki’s victory over Mr. Cuomo, a liberal icon in a largely Democratic state, could be in his mind as he looks to the next presidential election. Yet political observers said the conservative fiscal and liberal social views that appealed to New York voters who elected Mr. Pataki are not an appealing mix for the Republicans who twice sent President Bush to the White House.

“It’s very hard for me to see a George Pataki presidential candidate,” Mr. Zogby said. “I just don’t see a fit yet. He’s been governor of this state for 11 years, and he’s still enigmatic to voters. He’s also from the wrong state, is pro-choice, pro-gun control, and pro-gay marriage or at least -civil unions. That wouldn’t kill his chances, but John McCain and Rudy Giuliani are probably in the race, and those guys really suck a lot of the oxygen out of the room.”

Still, the emergence in polls of Mayor Giuliani, another Republican with liberal social views, as the top contender for the 2008 Republican nomination could be viewed as an encouraging sign for Mr. Pataki. If Mr. Giuliani can generate support in the heartland, a Republican strategist, Rich Galen, said, then Mr. Pataki might think he is capable of doing the same.

“I don’t think it’s any steeper of a climb for Pataki than it is for anyone else who is a legitimate contender,” Mr. Galen said. “You have to look at New York. It’s not like running from Delaware. It’s a huge state with a widely diverse economy and a widely diverse electorate. He’s won the general election there three times, and part of doing this is knowing how to do it.”

If Mr. Pataki challenges the conventional wisdom to pursue the White House, yesterday’s speech contained hints of his platform. Beginning with a reference to the terrorist attacks and following with a checklist of conservative fiscal policies he has pursued in office, the governor laid out the groundwork for a campaign centered on patriotism, fiscal restraint, and environmentalism.

Officials at the Republican State Committee chose yesterday to focus on the past. In a statement, the committee’s chairman, Stephen Minarik, said Mr. Pataki’s decision was reason to celebrate “the incredible legacy of New York’s greatest governor.” Mr. Minarik mentioned a number of the governor’s accomplishments, saying nothing of the future.

The state politician who is perhaps most eager in looking to the future after Mr. Pataki’s announcement this week is Mr. Spitzer. In a brief statement, the attorney general called the governor “a dedicated public servant,” adding, simply: “I look forward to working with him for the remainder of his term and wish him all the best in the future.”