DENVER — Brushing aside one final fevered push from her supporters, Senator Clinton made her latest public bid for party unity yesterday with a dramatic entrance into the Democratic convention hall, moving to cut off a roll call vote and officially nominate her chief rival, Senator Obama of Illinois, for the presidency.

The appearance by Mrs. Clinton capped a day of uncertainty and high emotions as Democrats here prepared for a convention floor vote that some worried would expose anew the divisions wrought by the party’s protracted, hard-fought primary. The former first lady, escorted by Governor Paterson and Senator Schumer, entered the Pepsi Center shortly before 6 p.m. Eastern time and about two-thirds of the way through the roll call of states.

Although clearly choreographed, the move caught the convention crowd by surprise, and a roar erupted as the image of Mrs. Clinton slowly making her way to the New York delegation appeared on television monitors throughout the arena.

“Madam Secretary, on behalf of the great state of New York, with appreciation for the spirit and dedication of all who are gathered here, with eyes firmly fixed on the future in the spirit of unity, with the goal of victory, with faith in our party and our country, let’s declare together in one voice, right here, right now, that Barack Obama is our candidate and he will be our president,” Mrs. Clinton said, after being introduced by the state Assembly speaker, Sheldon Silver.

She moved for the convention to suspend its roll call and nominate Mr. Obama by acclamation, but not before ensuring that her historic candidacy would officially be recorded. “All votes cast by the delegates will be counted,” she said to cheers. “I move that Senator Barack Obama of Illinois be selected by this convention by acclamation as the nominee of the Democratic Party.”

Mr. Schumer, standing behind Mrs. Clinton, then began chanting, “Hillary, Hillary,” and as his voice was captured by the microphone, the chant spread throughout the hall.

The move by Mrs. Clinton came a few hours before her husband addressed the convention last night, and it made for a historic moment as Mr. Obama officially became the first African-American to hold the presidential nomination of a major party.

The roll call vote through 32 states and territories was lopsided in Mr. Obama’s favor as delegates peeled away from Mrs. Clinton, a reflection of the increasing party unity that belied the closeness of the primary race this spring. Three states won by Mrs. Clinton earlier this year — Arkansas, New Hampshire, and New Jersey — unanimously cast their lot with Mr. Obama. In Indiana, where Mrs. Clinton won a razor-thin primary in May, the state delegation voted for Mr. Obama, 75-6.

Though the roll call was largely symbolic, a tighter result may have deepened the impression that the party remains divided heading into what is shaping up as a close general election battle. A Democratic Party spokeswoman, Natalie Wyeth, said results for the states, including New York, that were not announced on the floor were still being tallied last night.

Despite the show of unity on the floor, the lingering strength of support for Mrs. Clinton was on display earlier in the day, when she addressed a hall packed with hundreds of her delegates, who let out a loud “No” when she officially released them from the pledge to vote for her.

Speaking at a convention hall about a mile from the Pepsi Center, she said she had cast her vote in the morning for Mr. Obama, but she gave no further instructions for the roll call. “I’m not telling you what to do,” she told her delegates, “because you’ve come here from so many different places and made this journey and feeling in your heart what is right for you to do.”

In interviews yesterday, Clinton delegates cited several reasons explaining their decision to vote for Mrs. Clinton in the roll call, even as Mr. Obama’s nomination was assured. Some cited a deep loyalty to Mrs. Clinton, while others said they felt bound by their commitment as pledged delegates who had campaigned for the job on the promise that they would not waver. “I told them I would stick, and I stuck,” a Clinton delegate from Utah, Connie Nielsen, said.

Carol Ann Aliosi of Massachusetts said she felt some pressure from party officials to vote for Mr. Obama yesterday, but she held out for Mrs. Clinton. “She not only earned my vote but she deserved my vote today,” she said.

Two Obama delegates who had attended Mrs. Clinton’s rally with her delegates praised her speech but said they wished she had urged her delegates to vote for Mr. Obama in the roll call. “She left it a little open,” Lakeith Moore of Texas said. He also said he wanted to hear a more specific endorsement of the Illinois senator, particularly on the issue of national security. “If she was a little more concrete in her approval of Obama, that would put a lot of the confusion to rest,” he said.

Mr. Moore was speaking before Mrs. Clinton’s dramatic appearance at the convention, which may have gone further in soothing the concerns of Mr. Obama’s supporters. After Mrs. Clinton ended the roll call, Mr. Schumer took the stage and said that those Democrats who were proud to back Mrs. Clinton were now “equally proud to support Barack Obama.”

Mr. Schumer, speaking as the arena was still buzzing over the theatrics of Mrs. Clinton’s entrance, delivered what was largely a fund-raising pitch for the Democratic Senatorial Campaign Committee, which he heads.

He warned that without a larger Democratic Senate majority as president, Mr. Obama might have to “pare back the breadth and strength of what he proposes.”

In hard-hitting remarks, he characterized Senator McCain and the Republicans as obstructionists. When Mr. Obama wins, Mr. Schumer said, Mr. McCain will go back to the Senate, “and he and his friends will go back to saying no, no, no, to the change we so desperately need.”

With the political climate favoring their party, Democrats are eyeing a filibuster-proof 60 seats in the Senate, although that prospect is considered a long shot. “The opportunity is too great, the stakes too high to allow President Obama’s agenda to be blocked by the special interests and their allies in the Senate,” Mr. Schumer said.

Earlier in the day, Mrs. Clinton addressed a health care forum, where she spoke about her signature domestic policy issue and urged Mr. Obama to push for a universal coverage plan within the first 100 days of a new administration.