The election board deprived an ally of Mayor Harold Washington of a majority in an aldermanic election, throwing into doubt whether the mayor can gain control of the City Council for the first time since his 1983 election.

The Board of Elections Commissioners decided to count 10 write-in ballots for a minor candidate in the March 18 election, increasing the number of valid votes enough to drop Luis Gutierrez's total below 50 percent.

To avoid a runoff, an aldermanic candidate must receive 50 percent of the vote plus one.

Gutierrez holds a 20-vote margin over Manuel Torres, an ally of Edward Vrdolyak, who leads a majority bloc on the council that often has thwarted Washington's plans.

The Municipal Officers Canvassing Board, which certifies winners of city elections, has yet to decide whether all the votes for the minor candidate, Jim Blasinski, should be included in its certification of results.

Torres has asked the courts to force the elections commissioners to count the write-in votes, found during a recount. His most recent request was denied yesterday by a circuit court judge; an appellate court then denied an emergency appeal by his attorneys and refused to extend a stay barring certification of Gutierrez's victory.

But at almost the same time, the elections board voted to include 10 write-in ballots in Blasinski's total -- enough to force a runoff between Gutierrez and Torres.

A Gutierrez victory, coupled with the expected win by mayoral ally Marlene Carter in a runoff election April 29, would produce a 25-25 deadlock in the council, with the mayor casting the tie-breaking vote.