Senator Clinton is one step closer to becoming the Democratic nominee for president now that Mark Warner, the former governor of Virginia, has dropped out of the race.

Mr. Warner’s early departure from the 2008 Democratic primary, which he announced yesterday after months of traveling the country to test the political waters, eliminates a formidable threat to Mrs. Clinton.

“This is good news for Senator Clinton and it’s good news for a less rambunctious Democratic primary in 2008,” one Democratic political consultant, Hank Sheinkopf, said. “It means there is one less significant player in the field that could bring problems and that could then help the Republicans in the general election.”

Mr. Warner, a centrist Democrat who was term-limited out of the governor’s mansion in the Republican state of Virginia with high approval ratings, was billing himself as the most electable candidate in the Democratic pack.

At fund-raisers from New York to Iowa, he was carving out the role of the anti-Hillary, the candidate with the best chance of winning traditionally Republican states. He said the party needed someone with broader appeal to take back the White House.

His decision to exit the race surprised many who viewed him as a challenger who could do damage to Mrs. Clinton from his more conservative perch. Yesterday pundits wondered what the decision was about. A looming scandal? A reality check that he would be up against Mrs. Clinton’s vast political network and fund-raising machine?

But Mr. Warner, who co-founded Nextel and made a personal fortune as a venture capitalist, said simply: “At this point, I want to have a real life.”

“Anytime a serious contender drops out that helps the front-runner,” Steve Elmendorf, deputy campaign manager for Senator Kerry’s 2004 presidential campaign, told the Associated Press.

“Warner would have been perhaps the strongest, or certainly one of the strongest, candidates to become the anti-Hillary,” Mr. Elmendorf said.”This also will help somebody who’s looking at that role.”

While many Democratic analysts echoed that refrain, a professor of political science at the University of Virginia, Larry Sabato, said the calculus was simplistic.

“It’s classic inside the Beltway thinking,” he said. “They always assume that any development that eliminates a candidate helps the front-runner. It’s extremely simplistic.”

Mr. Sabato, who has known Mr. Warner for years and got a call from the former governor before the announcement, predicted that the Virginian’s supporters would disperse.

“They’ll scatter,” he said. “The preponderance of them will not pick Hillary Clinton. They were with Mark Warner because they did not want Hillary to be the nominee. That hasn’t changed.”

Senator Bayh of Indiana is seen as the most likely to step into centrist spot Mr. Warner was occupying. Other Democrats said to be considering a run are: Governor Tom Vilsack of Iowa; Governor Bill Richardson of New Mexico; the party’s vice presidential candidate in 2004, John Edwards; Senator Kerry; and, possibly, Vice President Al Gore. Senators Biden of Delaware and Feingold of Wisconsin are also possible contenders.

But with her national profile and fat war chest, Mrs.Clinton has a significant head start. She has raised more than $35 million for what many believe is a shoo-in re-election. Her leftover cash can be transferred to a presidential committee.

The executive director of RealClearPolitics.com, Tom Bevan, said Mr. Warner’s departure would make Mr. Bayh a more legitimate candidate, particularly because he has a stronger foreign policy resume than Mr. Warner.

“There is room for maybe one challenger to Hillary’s right and perhaps one to his left,” Mr. Bevan.

Although Mr. Bayh could take on the position of the moderate Democrat, he joined the most left-wing members of his party in voting against President Bush’s nominations of Samuel Alito and John Roberts to the Supreme Court.

Mr. Sabato said Mr. Warner’s decision is a net negative for Democrats.

“It’s a bad day for Democrats,” Mr. Sabato said. “Republicans are delighted with this development. They were afraid of Warner. They know what he could have done. He would have put together a coalition, including some business groups that would have been very difficult to beat in a general election.”

Mr. Warner is pro-choice, but favors restrictions on late-term abortion and thinks parents should be notified when a minor goes in for an abortion.

Mrs. Clinton, who has let other people speculate on her presidential ambitions as she runs for re-election, praised Mr. Warner during a campaign appearance in Syracuse.

“I respect his decision,” she said. “It’s such a personal decision. He’s been a tremendous public servant, and I hope we haven’t seen the last of him in Democratic politics and on the national stage.”

She also ramped up her criticism of the Bush administration’s handling of the war in Iraq, saying the “world would breathe a sigh of relief” if Mr. Bush replaced Defense Secretary Donald Rumsfeld.

Senator Kerry issued a similar statement: “I have great respect for Governor Warner and his service to Virginia and the Democratic Party. Anyone who has wrestled with this decision knows how hard it is.”

Meanwhile, during a conference call with supporters last night, Mrs. Clinton’s staff said turnout would be crucial in her election on November 7.

Analysts are already preparing to pore over the election results. Mr. Sheinkopf said a strong win, with support from more moderate factions of the Democratic spectrum, would signal that the rest of the country is ready for Mrs. Clinton.