The Chicago Tribune-WGN poll indicated 49 percent of voters said they supported Emanuel to 19 percent for Gery Chico.
Former U.S. Sen. Carole Moseley Braun was third with 10 percent and City Clerk Miguel del Valle had 8 percent, the poll indicated.
To win outright Feb. 22, a candidate must garner more than 50 percent of the vote. If no one reaches that threshold, the top two vote-getters square off April 5.
Results are based on surveys of 718 registered voters Saturday through Wednesday. The margin of error is 3.7 percentage points.