Finishing off an election that was canceled amid the Sept. 11 terrorist attacks, New Yorkers nominated Republican billionaire Michael Bloomberg for mayor Tuesday and sent two Democrats to a party runoff.

Bronx Borough President Fernando Ferrer and city Public Advocate Mark Green ran nearly even in Tuesday's Democratic primary, sending the race to an Oct. 11 runoff. Bloomberg, the financial media entrepreneur, sailed to an easy victory in the Republican primary.

With 80 percent of 5,630 precincts reporting early Wednesday, Ferrer had 228,659 votes, or 36 percent, to Green's 196,175 votes, or 31 percent. Candidates needed 40 percent of the vote to avoid a runoff.

Bloomberg, who has already spent more than $20 million of his own money on the race, easily defeated former congressman Herman Badillo. With 80 percent of precincts reporting, Bloomberg had 37,999 votes, or 72 percent, to Badillo's 14,941 votes, or 28 percent.

The winners of each primary meet Nov. 6.

However, the candidates, who fought to emerge from Republican Mayor Rudolph Giuliani's shadow during the campaign, now face the possibility that he might try to extend his term or seek re-election.

Exit polls suggested there was considerable support for Giuliani, whose handling of the crisis has been wildly applauded. About 40 percent of Democrats said they would vote for him if he found a way to run in November, while 80 percent of Republicans pledged to back him.

The unofficial returns did not include at least 15,000 absentee ballots or write-in ballots, all of which will be counted later. Exit polling of Republican voters indicated about 15 percent wrote in a candidate's name — presumably Giuliani — which is not enough to affect the primary's outcome.

Giuliani, who has served two terms and is forbidden by law from seeking a third, has not ruled out trying to stay on as mayor, saying he needs more time to think about his political future.

But most voters refused to let terrorism change the decisions they had made before the attack, exit polls showed. Voters largely stuck with the mayoral candidates they backed before the attack, and many continued to rate education over terrorism as their top concern, according to an exit poll conducted by Edison Media Research.

Ferrer, 51, is seeking to become the city's first Hispanic mayor. He asked campaign supporters for a moment of silence in honor of the people still missing since the twin towers collapsed.

"Rarely in our history have we seen so much will and determination in the city and the country," Ferrer said. But Ferrer said other issues he has made central to his campaign, such as education, must not be neglected.