NEW YORK (AP) _ Gov. Mario Cuomo breezed to a third term over splintered Republican opposition Tuesday, maintaining his standing as a leader of the Democratic Party and potential presidential candidate for 1992.

While Cuomo has consistently maintained that he ''has no plans to run for president and no plans to make plans,'' Democratic leaders said a re-election victory would increase interest in him.

''He'll be under more pressure than he's ever been under before,'' Robert Strauss, a former Democratic national chairman, predicted last week.

Cuomo's opposition included millionaire economist Pierre Rinfret, the Republican challenger who was an unknown in New York politics six months ago, and Conservative Party nominee Herbert London.

With 19 percent of precincts reporting, Cuomo had 389,863 votes, or 49 percent, to 193,809 votes, or 24 percent, for Rinfret, and 181,166 votes, or 23 percent, for London.

In the final two months of the campaign, the outspoken, underfunded Rinfret spent almost as much time bashing prominent Republicans as he did attacking Democrat Cuomo. Rinfret's paltry campaign war chest reflected GOP displeasure.

With Rinfret's campaign in shambles, Republicans scrambled to produce enough loyal voters to keep London from finishing second. By finishing third, the GOP could lose its second-row ballot spot in New York elections for at least the next four years.

Also threatened by a possible low Republican turnout was GOP control of the state Senate.

A Marist College Institute for Public Opinion poll released last week had Cuomo the choice of 61 percent of those surveyed with Rinfret and London tied for second place at 11 percent each.

Of New York's 34 congressional members, 21 Democrats and 13 Republicans, five ran unopposed and the others were favored to win re-election.

On Staten Island, voters decided whether to start a process that could lead to secession for the smallest of New York City's five boroughs.

Meanwhile, Cuomo asked voters statewide to approve a $2 billion environmental bond act that would provide $800 million to buy land and $625 million for garbage problems.