Giuliani Gains Ground in New York. The former US attorney, a Republican, wins the support of New York's Liberal Party. MAYORAL RACE

EVEN before he officially announces his candidacy, Rudolph Giuliani is assured that his name will be on the ballot this fall when New Yorkers vote for mayor. Last Saturday, the New York Liberal Party endorsed Mr. Giuliani, a Republican.

The Liberal endorsement, says Richard Ravitch, a Democrat who will announce his own candidacy for mayor in May, ``should make the Democrats realize they are facing a formidable opponent.''

The drawing card for the former US Attorney for the Southern District of New York is his reputation. He is known as a tough prosecutor, not afraid to pursue corruption. Among his more celebrated cases was the corruption conviction of Stanley Friedman, the Bronx Democratic leader. Such scandals have tarnished the image of Mayor Edward Koch, who is seeking a fourth term.

Mr. Giuliani also has national recognition since he instigated the government's crackdown on insider trading on Wall Street. In fact, this week the former US attorney will be in Tokyo advising the Japanese on their own Recruit Cosmos stock scandal.

With strong name recognition, it is widely expected that Giuliani will beat his chief Republican opponent, Ronald Lauder, heir to the Est'ee Lauder fortune. The primary is Sept. 12.

The Giuliani rise has already sparked additional combativeness in Mayor Koch who also faces a tough challenge for the Democratic nomination from David Dinkins, Manhattan Borough president; Ravitch; and City Controller Harrison Goldin.

Referring to Giuliani's stand on abortion, the mayor says, ``I don't see Giuliani marching around in support of Roe v. Wade.'' (Roe v. Wade is the 1973 landmark lawsuit that legalized abortion.) Giuliani explains that his Roman Catholic background shapes his own views. But he says he would uphold the constitutional guarantee of a woman's right to choose an abortion.

Last Friday, the National Organization for Women (NOW) in New York denounced the coming Liberal Party endorsement because of Giuliani's views on abortion. ``We are very distressed at their decision,'' says Francoise Jacobson, NOW-NYC president.

Despite such criticism, Giuliani remains popular. Lee Miringoff, of the Marist Institute of Public Opinion, says his poll in the fall showed Giuliani beating Mr. Koch by 10 points. ``Since then Koch has been pretty flat,'' says Mr. Miringoff who adds that the Liberal Party endorsement should leave Giuliani well positioned. ``It gives Giuliani a chance to pick up voters who otherwise would not want to vote on the Republican side. ''

In fact, state Sen. Roy Goodman, the city's Republican Party head, says a fusion ticket is vital to elect a Republican mayor. Democrats outnumber Republicans by a 5-to-1 margin. ``Without a fusion ticket, a Republican has a snowball's chance in Panama in August of being elected mayor,'' says Senator Goodman.

To round up votes and money, Giuliani has been putting together a professional organization. He has hired Rich Bond, Russell Schriefer, and pollster Robert Teeter. Mr. Bond was political director of the Bush campaign, working directly under Lee Atwater; Mr. Schriefer was Bush's mid-Atlantic political director. Mr. Teeter was Bush's pollster. Schriefer, Giuliani's campaign director, says Giuliani has raised well over $100,000 ``without raising a finger.'' More money may be on the way since the Friends of Giuliani campaign is in the process of putting together a solicitation. Although there will be no particular criteria, ``we won't take money from crooks,'' Schriefer says.

But Giuliani will take money from Wall Street financiers - the same people he has sometimes characterized as excessively greedy. In fact, Schriefer says Giuliani will be back on Wall Street again soon. Instead of handing out indictments, the former prosecutor will be collecting endorsements. ``While there has been some concern about the things he did as US attorney, it has not translated into a lack of support,'' Schriefer says.