CHICAGO (AP) _ A judge ruled Friday that a special election should be held next year to choose a successor to the late Mayor Harold Washington, a decision that drew cheers from courtroom spectators.

Cook County Circuit Judge Eugene Wachowski had to call for order to quell the jubilant reaction. But a spokesman for the losing side, which backs a 1991 election date, vowed to appeal to the Illinois Supreme Court.

Alderman Timothy Evans, an opponent of Mayor Eugene Sawyer, called the ruling a victory for the people of Chicago. Asked whether he'll be a candidate in the next election, Evans said, ''You'll have to tune in to see.''

There was no immediate comment from Sawyer, who was not directly involved in the case. Mayoral spokesman Monroe Anderson was not in his office.

The City Council chose Sawyer over Evans at a raucous, all-night meeting a week after Washington, the city's first black mayor, died of a heart attack Nov. 25.

Though both Evans and Sawyer are black, Sawyer was elected primarily through the backing of the city council's old-guard white aldermen. Hundreds of Washington and Evans loyalists had thronged City Hall, protesting that ''back-room deals'' were cutting voters out of the decision-making process.

''It's a marvelous, marvelous victory for all of those citizens ... who came down to La Salle Street and stood in the City Hall rotunda imploring their aldermen to listen to them,'' said a smiling Evans as he emerged from Friday's hearing.

In his ruling, Wachowski said he believed state law clearly granted the city Board of Elections Commissioners authority to call a special election in the spring of 1989, as the board did earlier this week.

Attorney Russ Stewart, representing a group called United Citizens of Chicago and Illinois, had argued that Sawyer was properly elected by the City Council and should be allowed to serve until 1991, when Washington's second term would have ended. The group denied any ties to Sawyer.

But attorneys for a group calling itself The Coalition To Let The People Decide in 1989 argued successfully that Illinois law clearly requires a special election if a municipal officer dies or resigns with more than 28 months remaining in his or her term.

''The question before you,'' attorney Tom Johnson told the judge, ''is whether the voters, the people in the neighborhoods, will have a chance to participate in deciding who will govern the city of Chicago for the remainder of (Washington's) 48-month term.''

Former GOP mayoral candidate Kenneth Hurst, president of the United Citizens, said he would appeal Wachowski's decision. He described his group as a non-partisan watchdog organization seeking fair government.

Alderman David Orr, who served briefly as interim mayor after Washington's death, called the ruling ''a defeat for Mayor Sawyer in that he mistakenly let his followers say they favored 1991.''

''He let the public believe he preferred 1991, and I think that was a mistake, because you never want to tell the public they don't have the right to choose who their leader will be,'' Orr said.