"We need to have a mayor who can speak, a mayor who can think on his feet a mayor who can change course in this city," said Mr. Giuliani, the Republican-Liberal candidate, in a speech to some of his staunchest supporters at the Sheraton New York Hotel and Towers.

Yesterday, one day after he released an ad criticizing Mr. Giuliani on the abortion issue, the Mayor began broadcasting another commercial that accused his rival of waffling on gun control and of being linked to the Reagan Justice Department that tried to "turn back the clock on civil rights."

Mr. Giuliani condemned the ads as "nasty personal attacks" and pledged to his supporters to keep his campaign focused on issues and management style. Responding to the Opposition

The Mayor's aides say their latest ad is part of their deliberate effort to counter weeks of commercials in which Mr. Giuliani attacked conditions in the city -- and thus implicitly the Mayor -- without naming him. They want to frame the election as a contest between Democrats and Republicans, something they contend President Clinton was also trying to do last weekend in his speech supporting the Mayor, in which Mr. Clinton worried that too many New York Democrats might be unwilling to support the Mayor in part because of his race.

Asked why the Mayor should be so strongly on the offensive if they believe the latest polls that show him even or ahead, mayoral advisers said they believed they have scored so far by chipping away at Mr. Giuliani's record and intend to continue. They vowed not to make "personal attacks," saying the Mayor would not allow that.