Democrats Press Thompson to Forsake a Runoff New York City's Democratic power brokers moved Wednesday to prevent a combative sequel to the party's primary for mayor, as union officials and political leaders rallied around the front-runner, Bill de Blasio, and urged the second-place finisher, William C. Thompson Jr. to end his quest for a runoff election. On a day of back-room maneuvering and deal-making, Mr. Thompson's own inner circle appeared divided over how, or even whether, to proceed. Mr. Thompson vowed to press on, but the chairwoman of his campaign said Mr. de Blasio had won a "clear victory" and suggested the race was over. "I don't think there's much appetite within the Democratic Party to have a fight here," Merryl H. Tisch, the chairwoman, said in a telephone interview. Mr. de Blasio, eager to cement his status as the Democratic nominee, acted to project an air of inevitability by wooing labor unions that had supported his rivals. Several unions that snubbed Mr. de Blasio in the primary prepared to throw their support behind him at a rally on Thursday, arguing that it was in the best interests of their members. A longtime Thompson ally, the Rev. Al Sharpton, encouraged him to give up his campaign, and an influential labor group, the Hotel Trades Council, endorsed Mr. de Blasio. "It's time for working people and Democrats to unite behind our next mayor, Bill de Blasio," said Josh Gold, political director of the Hotel Trades Council. Mr. Thompson found some measure of hope in the uncertain election outcome. With 99 percent of precincts reporting, Mr. de Blasio had won 40.3 percent of the vote, just over the 40 percent required by law to avoid a runoff, but there were more than 16,000 paper ballots that have not yet been counted. "I want to make sure that every voice is heard, that every vote is counted," Mr. Thompson told reporters after attending a Sept. 11 service at the Firemen's Memorial in Riverside Park. But Mr. Thompson, who won 26.2 percent of the vote, was harboring no illusions about the long odds against him, according to those close to him. And there were strikingly few calls from Democratic leaders for him to fight on. "He should get out in the name of unity," Mr. Sharpton told two elected officials close to Mr. Thompson, according to a person told of the conversation. Mr. Sharpton, who is one of the city's most prominent black leaders, argued that Mr. Thompson's poor performance with black voters on Primary Day boded poorly for him in any runoff, when voter turnout might be even lower. Mr. Sharpton, who had already disappointed Mr. Thompson by staying neutral in the primary, invited Mr. de Blasio onto his MSNBC show on Thursday night. Democratic Party officials are eager to determine their nominee in order to mount the strongest possible campaign against the Republican candidate, Joseph J. Lhota. Although the city's voters are overwhelmingly Democratic, they have not elected a Democrat as mayor since 1989. State Assemblyman Keith L. T. Wright, co-chairman of the state Democratic Party and a longtime friend, suggested that, for the sake of party unity, Mr. Thompson would not mount a challenge. "Knowing Billy the way I do, ultimately whatever his decision is, he's going to do what's good for the Democratic Party," said Mr. Wright, whose friendship with Mr. Thompson dates to when they were undergraduates at Tufts University. "He knows that we've been suffering under Republican mayoralties for the past 20 years," he added. On Wednesday night, Mr. de Blasio won the endorsement of Local 32BJ of the Service Employees International Union, which represents doormen, and the Retail, Wholesale and Department Store Union. Both unions, like the Hotel Trades Council, supported Christine C. Quinn, the City Council speaker, in the primary. "Union members across this city have responded to Bill de Blasio's articulation of the struggles of every day New Yorkers," said Vincent Alvarez, president of the New York City Central Labor Council, an umbrella organization that represents more than one million unionized workers. Mr. de Blasio and Mr. Lhota both declined to discuss politics on Wednesday because of the Sept. 11 anniversary. "We'll talk later," Mr. de Blasio told reporters outside his house in Park Slope. Mr. Lhota, brushing past reporters outside his apartment in Brooklyn Heights, did not even greet those seeking comment. Democrats who have been telling Mr. Thompson to abandon his bid say that he faces several daunting challenges. One person who raised thousands of dollars for him said it was unlikely that Mr. Thompson would be able to raise substantial money for a runoff, because most people believe that Mr. de Blasio would trounce him. But some members of Mr. Thompson's team believe that there were irregularities in polling places that might have affected the results. And one person said Mr. Thompson had long relished defying the predictions of the city's political world. "He is not the kind of guy to give up," this adviser said. If there's the slightest chance that he can win, he'll take it. Assemblyman N. Nick Perry, a Brooklyn Democrat who is backing Mr. Thompson, said it was reasonable for Mr. Thompson to wait for the remainder of the votes to be counted before he made a decision on whether to move forward. "De Blasio does seem to have the momentum in his favor," Mr. Perry said. But politics is a very unpredictable and crazy game, and today things can happen and the next day the whole world is different, and your castle comes falling down. Javier C. Hernández, Nate Schweber and Julie Turkewitz contributed reporting.