CHICAGO, NOV. 28 -- The way Jesse L. Jackson described it, he was simply "the senior member of the family" who had returned home in a time of crisis "to convene the family."

But today Jackson, a candidate for the Democratic presidential nomination, looked very much like a kingmaker in the confusing world of Chicago mayoral politics. And most of the city's black political structure treated him that way.

Jackson, who interrupted a fact-finding trip to the Middle East to return here, moved during his first 20 hours in the city to broker the selection of a successor to Harold Washington, the city's first black mayor, who died Wednesday of a heart attack.

Jackson did not achieve that goal immediately, but he certainly made his presence felt.

He first caucused with Chicago's three black congressmen, two aldermen seeking to succeed Washington and other black leaders who greeted him at O'Hare International Airport as though he were a visiting head of state.

After viewing Washington's body, which is lying in state at the city-county building, Jackson brought the city's 22 black and Hispanic members of the City Council together with scores of community leaders in his presidential campaign headquarters and exhorted them to unify behind a single mayoral candidate.

That four-hour meeting ended at midnight Friday without reaching a consensus. Nine hours later, Jackson presided over a long and emotional memorial service for Washington at the headquarters of Operation PUSH, the civil-rights group Jackson founded. The service attracted thousands of mourners and most of the city's black politicians.

The three black aldermen who are vying for the mayoralty sat beside the lectern as Jackson spoke.

"We can survive in our own little patch. But we can't win," Jackson said. "Leaders get bigger than your patch. Leaders get bigger than your district. Leaders get bigger than your ward. Leaders get bigger than your race."

Jackson embraced a Democratic Party slate Washington had put together weeks before his death and vowed to make it his own. "Today we weep, but we must keep the team together," Jackson said. "Harold's latest slate is a monument to his vision of the city and urban America."

Jackson avoided publicly endorsing any candidate, but it was apparent that he was subtly promoting the candidacy of Alderman Timothy Evans, who was Washington's floor leader in the City Council.

Evans, 43 and a lawyer, was given a chair closer to the crowd and the television cameras than his two rivals, Aldermen Eugene Sawyer, 53, and Danny K. Davis, 45. Evans was given a favored position on the program. And when the group raised their clasped hands together, Evans was at Jackson's right, holding his hand.

Afterward, Jackson said at a news conference not to "read anything into whose hand I hold." But he said he noted "there is a spark in there for Evans" and "a chemistry between Tim Evans and the people."

Jackson also spoke warmly, but in less favorable terms, of the other leading black candidate, Sawyer. "He has a great capacity to make a lot of people feel at ease and comfortable. He has staying power," Jackson said of Sawyer.

This was a recognition of the political realities, and it gave Jackson some maneuvering room. The 50-member City Council is to choose an acting mayor, who will serve until the next municipal elections, which are in April 1989. Neither Evans, who is supported by reform elements that backed Washington, nor Sawyer, who is favored by old party regulars, has anywhere near the 26 votes needed to win.

Sawyer led Evans in most informal tallies, which indicated that he is getting the support of from nine to 13 other black aldermen. Evans is drawing support from white liberals and Hispanics as well as a few blacks.

As white aldermen met to plot strategy on the city's North Side, Jackson and his allies today tried to build black public support for Evans as Washington's political heir. Jackson planned to continue this effort Sunday by speaking at black churches.

"When Harold Washington was alive, there were 27 votes for reform. And we know that the city of Chicago expects 27 votes for reform when that City Council reconvenes," Alderman Luis Gutierrez said in introducing Jackson. "The city of Chicago is saying make no deals . . . do not cross the line against reform, don't betray Harold Washington's memory."

Jackson has been criticized by some Sawyer supporters for interfering in the succession battle. Gutierrez defended him today, saying: "He is here to bring us together. Just like when we lose a member of the family, we look to someone for strength, we look for someone to clear the skies."

As Chicago's two best known black leaders, Jackson and Washington had a sometimes uneasy relationship. Jackson was a major supporter of Washington during his first successful campaign for mayor in 1983, but Washington felt Jackson tried to claim too much credit.

The mayor backed Walter F. Mondale, not Jackson, for president in 1984. But Washington endorsed Jackson's 1988 presidential candidacy and had promised to campaign strenuously for him.

Chicago is a bastion of Democratic Party strength, and Jackson would like to have a friend in the mayor's office during the presidential campaign.

But Washington's death also gave Jackson the opportunity to establish himself undisputedly as the most powerful black leader in Chicago and a force to be reckoned with for the long term.

By adopting Washington's Democratic slate as his own, Jackson also gave himself an opportunity to expand his "rainbow coalition." The most controversial person on that slate is Aurelia Pucinski, whom Washington picked as the party's candidate for clerk of the Cook County Circuit Court over former mayor Jane Byrne.

Pucinski was one of the few whites who attended services at Operation PUSH. And Jackson repeatedly singled her out for praise.

Her father, Alderman Roman Pucinski, was a longtime Washington opponent, and his ward has long been a center of anti-black sentiment.

Washington's body is to continue to lie in state Sunday. A steady stream of mourners filed by the open coffin at a rate police estimated at 4,000 an hour. A riderless horse led the city's annual Christmas parade today as a tribute to the late mayor.

Washington, who was seven months into his second term, will be buried after a funeral Monday.