After four terms that will have spanned 24 years, Chafee, 76, said he wants to spend more time with his dozen grandchildren and reclaim his large family house in Warwick, where he is ready to tackle pesky junipers that have encroached on a favorite field.

Chafee's announcement was not entirely unexpected, but it was sudden. As if a dam had burst, the prospect of a rare open Senate seat attracted an immediate torrent of speculation and declarations of interest from Rhode Island's politicians.

Sources said Democratic U.S. Rep. Robert A. Weygand will definitely enter the race. Chafee's son, Republican Warwick Mayor Lincoln Chafee, confirmed that he is considering a bid. Providence Mayor Vincent A. Cianci Jr. said he will ponder running as an independent.

Whoever does jump in will have to get their money-raising and strategy gears turning fast. Based on past Senate races, a successful candidate will have to raise at least $2 million.

Weygand was said to be planning an announcement as early as this week. Lincoln Chafee said he will be deciding in a matter of weeks, but he would not discuss any specifics.

"Today is Dad's day," he said.

Limping slightly from an inflamed Achilles tendon, Senator Chafee made his announcement at a noon news conference in the State House, where his career took flight in 1962, when he barely won election to the governor's office.

A few dozen of his old political friends, including U.S. Court of Appeals Judge Bruce Selya, who was an adviser on that first campaign for governor, turned out to witness the waning of a historic public career. The senator was joined at the podium by four of his five children and a troop of grandchildren, who embraced him in turn when he arrived at the State House.

"Hi, Papa]" they said.

"I want to come home," Chafee told the gathering.

CHAFEE REFUSED to discuss his future during the impeachment trial in the Senate, where he led a band of New England centrists who denied their party a majority on perjury and obstruction-of-justice counts. It wasn't until after the impeachment votes that he decided he would not run again.

Few people knew what he would say about his future until yesterday morning, when he began making calls to prominent Republicans in Washington and Rhode Island. There were clues, however, not least of which was that he had not raised any money for a reelection bid.

After his announcement, Chafee received calls from dozens of powerful well-wishers, including President Clinton, who told Chafee he would have bet the senator would remain in Washington.

"He said, 'You're a good poker player,' " Chafee recounted in an interview.

(Before the day was out, the White House had released a statement that lauded Chafee for his work as a "tireless champion" of the environment.)

It was easy to see why many thought Chafee might remain. He is the state's most powerful Washington delegate and his clout is at a peak, a level of influence not only demonstrated by his high-profile role in Mr. Clinton's trial. He is chairman of the Environment and Public Works Committee and is the number-two Republican on the Finance Committee, positions that help him steer millions of dollars in federal projects to Rhode Island.

But Chafee said those very factors made it a great time for him to leave. He said he has no desire to remain in the Senate into his 80s.

"I'm not seeking to set some world record in age in this place," he said. "I've seen an awful lot of senators hang around here too long, where they've lost their steam."

CHAFEE HAS EMBODIED the ambitions of Rhode Island's heavily outnumbered Republicans for years. Educated at Deerfield Academy, Yale and Harvard, he tempered his aristocratic breeding with a folksy campaign touch. He also had a war record, fighting at Guadalcanal during World War II and returning to active duty during the Korean War. He won election over and over again in the heavily Democratic, working-class state despite his party label.

Chafee began his political career in 1956 as a state representative from Warwick. He ran for governor in 1962 in a race that wasn't decided until 24 days after the election; when all the mail ballots were counted, he had 398 more votes than Democrat John Notte.

Chafee left some big visual reminders of his tenure as governor. He built what is now known as the Claiborne Pell Bridge, insisting that motorists be able to see Narragansett Bay as they soared over Newport Harbor. He also mounted an aggressive public-spaces campaign, with the preservation of Colt State Park in Bristol as the centerpiece.

After he lost his bid for a fourth term as governor in 1968 (to Frank Licht, whose nephew, Richard Licht, Chafee defeated in a 1988 Senate race), Chafee moved to Washington as secretary of the Navy under President Nixon. He lost his first try for U.S. Senate in 1972, and then won in 1976, joining another WASP establishment figure in the Rhode Island delegation, Democratic Sen. Claiborne Pell, the man who had beaten him four years earlier.

The two widely respected senators represented the smallest state in the Senate together for two decades, until Pell retired in 1996.

In the Senate, Chafee has worked on health care, housing and the rights of the disabled. But it was on the environment that he made his biggest mark, becoming a powerful ally of such advocates as the Sierra Club and The Nature Conservancy as he worked for cleaner air and water, endangered species and on efforts to combat global warming.

Part of Chafee's public persona, what makes him a natural as leader of the Senate's 22-member Centrist Coalition, is his determination to avoid the kind of ham-fisted political assaults that make great sound bites but plenty of enemies.

Yesterday, he stayed true to those gentlemanly principles. Given the chance to criticize the partisanship that has taken over Senate debates, he refused - a good sport to the end.

"It's traditional to say it's become more nasty and more partisan and more biting; I don't think that's true," he said. "I will leave with great admiration for the Senate and the highest respect for a host of senators - Republican and Democratic."

A STRING of Rhode Island leaders heaped praise on the senator and said his influence in Washington and on the state's GOP would be sorely missed.

"It is really the end of an era, because (Chafee) has been a signature politician," said Judge Selya. "He has been a person whose whole ethos has been public service, not to accomplish a personal agenda or his own aggrandizement.

"One thing some of his colleagues in Washington probably find hard to understand is that someone who has a relatively safe seat and who is a powerful committee chairman would leave.

"It's all part of who John Chafee is," Selya said. "The power and the glory were never what motivated him and certainly would not motivate him to stay."

Governor Almond and former Gov. Bruce Sundlun, a Republican and a Democrat, gave typically bipartisan and glowing reviews of the senator's career and on his abilities to bring home federal pork.

Chafee couldn't keep Nixon from cutting back Rhode Island's Navy bases in the 1970s, but he has helped minimize further damage to the Navy's presence since, bolstering the Naval Undersea Warfare Center, Naval War College and the Naval Education and Training Center. Almond credited the senator with infusing the state with federal highway dollars that have saved the Department of Transportation budget from red ink.

Almond said that he got a firsthand look at Chafee's influence in Washington during trips to the Capitol to seek money for Rhode Island projects.

"It's just a marvel to see, privately, the great respect he is held in by senators of both parties," said Almond. "When you are a governor and you have John Chafee leading the way into the office of a senator, that really makes life easy for you.

"We're really going to miss this guy."

"In the history of this state, there are very few people who have contributed as much to public service as John Chafee has," Sundlun said. "In my judgment, he's at the peak of his game, and I hate to see him retire."

FOR REP. JOAN QUICK, R-Little Compton, chairwoman of the state Republican party, Chafee's announcement was nothing less than seismic. The departure of the state GOP's "patriarch," she said, leaves a huge hole at the top of the 2000 ticket.

Three hours after Chafee's press conference, the communications director of the Democratic Senatorial Campaign Committee, Michael Tucker, whizzed off a press release declaring, "This seat is ours."

Tucker cited the evidence: Both of Rhode Island's congressmen are Democrats. So is every elected general officer but Almond. Democrats hold a 42-to-8 majority in the state Senate and an 83-to-17 margin in the House.

But Quick looked around the room at Chafee's event yesterday and ticked off a quick list of possible Republican replacements, starting with Lincoln Chafee, who just won election to a fourth term as Warwick mayor.

She also mentioned former U.S. Rep. Ron Machtley, president of Bryant College; James Bennett, the GOP's candidate for treasurer last year; Bernard Jackvony, the former lieutenant governor, and former Cranston Mayor Michael Traficante.

She agreed that the GOP would have a better shot of holding Chafee's seat if it can avoid a primary. But, she predicted, "Even if we have a primary, the Democrats will have a more divisive primary than we do."

It does appear true that the potential for collision is greater as Democrats scramble for early footing.

Congressman Weygand is retaining consultants and has met with the Senate Democrats who can help him raise money. Secretary of State James Langevin has been eyeing a bid for months and says he will not be swayed by Weygand's decision. Former state Sen. Myrth York, who has suffered two defeats to Governor Almond, said she is enticed by the possibility of a Senate campaign.

About the only high-profile Democrat who specifically ruled out a Senate run was the one who might have the best shot: U.S. Rep. Patrick Kennedy.

Kennedy accepted the number-five leadership position in the House minority, chairman of the House Democratic Campaign Committee. He reiterated yesterday that the House is where he will remain, pinning his immediate political career to the party's hopes of seizing House control from the GOP.

Kennedy said he will also make a Senate victory for Rhode Island Democrats a top personal priority in 2000 but cautioned, "I don't think anybody is going to waltz into that seat. The stakes are too high."

With reports from John E. Mulligan, Journal Washington Bureau, and Jonathan Saltzman, Journal State House Bureau.