Chicago's election season had its official kickoff last week when Mayor Richard M. Daley (D) and 150 other candidates for city offices filed nominating petitions for next year's races.

"I'm proud of how far we have come in these 20 months, but I know there is still much more to be done," said Daley, who is finishing a two-year half-term that resulted from the 1987 death of Mayor Harold Washington (D).

Daley's announced challengers in the Feb. 26 Democratic primary are Alderman Danny K. Davis and former mayor Jane Byrne. The slated Republican candidate, police detective George S. Gottlieb, is not expected to mount a serious challenge in heavily Democratic Chicago.

To qualify for a chance to appear first on the ballot, candidates for mayor, clerk, treasurer and alderman in the city's 50 wards were required under a new state law to file petitions at the Chicago Board of Election Commissioners as soon as the office opened at 9 a.m. Monday. Top ballot positions will be determined by lottery on Dec. 26.

Aides for Daley filed his petitions; Byrne is still compiling petitions and plans to file early this week, and Davis, a consensus candidate of the black community, filed his petitions in person. "Ours is what one might call a people's campaign," he said.