Philip Boyle, a Republican state assemblyman from East Islip, appeared to defeat Democrat Rick Montano, a Suffolk County legislator from Brentwood, in what was expected to be the Island's most competitive race.
Long Island's other eight GOP incumbent senators appeared to be on the road to re-election, according to unofficial returns.
The 4th District was a seat Democrats were hoping to win to regain control of the Senate.
Statewide, Republican senators outnumbered Democrats 33-29. Redistricting added an upstate Senate seat this year that the Republican leadership hoped would solidify its control. Democrats would need to pick up three Senate seats to reach the 32-member majority.
Sen. Michael Gianaris (D-Queens), head of the Democratic Senate Campaign Committee, predicted that Democrats will have at least 32 seats in the Senate and said they were leading in two other races.
But Scott Reif, spokesman for the Senate Republicans, said, "We are confident once all the votes are in, we will retain our majority."
Boyle, 51, who has served two stints in the Assembly, had run a well-financed campaign against Montano, 62.
"It was a great win," Boyle said. "We can have a good time tonight, but first thing in the morning we have to roll up our sleeves and get to work."
Montano did not concede. His spokesman, Ivan Young, said, "We're going to wait for every vote to come in and then we'll assess where we're at and what our strategy is."
Suffolk Democratic chairman Richard Schaffer lamented Montano's likely loss. "The district enrollment gives us an edge but Republicans spent a lot, and sometimes money is difficult to overcome," he said.
Recent campaign disclosure reports show that Boyle, helped by $225,000 from the state Republican committee, had raised nearly $610,000 -- more than twice as much as Montano, who got just $12,000 from Suffolk Democrats.
Boyle, like the other Republican candidates on Long Island, has emphasized the party's cooperation with Democratic Gov. Andrew M. Cuomo in passing the 2 percent cap on tax levy increases by municipalities and school districts. He warned that Montano will side with city Democrats against Long Island interests.
Montano accused Boyle of running a "fear and prejudice" campaign against the city. He said he has worked with Republicans on the Suffolk County Legislature to control spending.
In Nassau, Democrat Ryan Cronin, an attorney from Garden City, had mounted an aggressive campaign against veteran Republican lawmaker Kemp Hannon, also of Garden City, in the 6th District, which runs from Garden City to Farmingdale. With almost all election districts counted, Hannon led Cronin by nearly 5,000 votes early Wednesday morning.
With Candice Ruud,
Patrick Whittle, Rick Brand
and Robert Brodsky