Democrats were on track to gain seats in the state Senate last night, moving Albany closer to being a one party town.

In the Senate, where Republicans have a 37-24 majority, Democrats were expected to narrow the gap by three to five seats. Democratic candidates defeated incumbent Republicans in New York City and Syracuse and claimed an open Bronx-Westchester seat that had been in the GOP column until Guy Velella went to jail earlier this year.

In the Assembly, Democrats hoped to maintain their already dominant majority of 103-47.

The leftward shift in the Senate makes it more likely that lawmakers will maintain or expand New York’s relatively high spending on health care, education, and other government programs, despite multibillion-dollar budget deficits in the years ahead. This, in turn, will exert upward pressure on tax rates.

The trend not only jeopardizes the job of the Senate majority leader, Joseph Bruno of Rensselaer County, it also further weakens the hand of Governor Pataki, a Republican, who saw 120 of his budget vetoes overridden by the Legislature last year. The minority leader, David Paterson of Harlem, has said he hopes to take control of the Senate within the next two or three elections.

This year, the Senate Democrats scored some of their biggest victories in New York City, after waging hard-fought campaigns in three districts.

In the 23rd District, covering parts of Brooklyn and Staten Island, Democrat Diane Savino, a social worker and union activist, defeated Republican Albert Curtis, a former commissioner of youth services under Mayor Giuliani.

With 100% of precincts reporting, Ms. Savino won, 36,859 to 21,629.

Ms. Savino will replace Seymour Lachman, a Democrat who is retiring at the end of the year.

In the 34th District, covering parts of the Bronx and Westchester, there was a three-way race to fill the seat formerly held by Velella, who pleaded guilty to bribery charges earlier this year. With 75% of precincts reporting, the Democrat candidate, Assemblyman Jeffrey Klein, was leading with 51% of the vote; the Republican, John Fleming, a former city police detective, had 35%, and the Independence and Conservative nominee, Assemblyman Stephen Kaufman, had 14%.

In the 28th District, the Democratic candidate, City Council member Jose Serrano easily defeated Senator Olga Mendez, a 26-year veteran who switched parties to join the Republican majority shortly after the 2002 election. With 100% of precincts reporting, Mr. Serrano won, 47,915 to 10,635

Democrats also stood a chance of winning two other seats: In a three-way race near Syracuse, challenger David Valesky was holding a narrow lead over the Republican incumbent, Nancy Larraine Hoffmann, in early returns. And in Westchester, an incumbent Republican, Nicholas Spano, was in a tight race against a Democratic challenger, Andrea Stewart-Cousins.

The fighting between Ms. Savino and Mr. Curtis was particularly fierce, including a last-minute flap over a flier in support of Mr. Curtis by Independence Party activist Lenora Fulani.

“I’m not asking you to vote for Al Curtis because he’s black,” Ms. Fulani wrote in the flier. “I’m asking you to vote for Al Curtis because you’re black. Make sure you vote independent to send a strong message that our votes can’t be taken for granted.”

When Democrats accused Ms. Fulani and Mr. Curtis of injecting racial politics into the campaign, black members of the Independence Party demanded an apology from the Savino campaign.

“I’m not playing the race card,” Ms. Fulani told The New York Sun yester day. “I’m doing what I’ve always done, which is to speak openly to the black community about becoming independent.”

“I’ve been black in America all my life,” she said. “I’m not about to have Diane Savino or the Democratic Party tell me how I can or cannot talk to the black community.”

Democrats also accused the Curtis supporters of spreading rumors that Ms. Savino is a lesbian, to undermine her support among Orthodox Jews in Boro Park.

“This has really been one of the nastiest campaigns I have ever seen, crossing all the lines of what is morally and politically appropriate,” said a supporter of Ms. Savino, Assemblyman Dov Hikind.

Democrats also raised objections to Republican tactics in the race between Mr. Spano and Ms. Stewart-Cousins, a member of the Yonkers City Council.

At polling places in Yonkers, Democrats complained that votes had been recorded on machines before the polls opened and that voters were improperly asked to show identification outside of polling places.

Yesterday afternoon, Democrats obtained a judge’s order to impound voting machines pending a court review. “The tactics made it very clear they were going to try to disrupt this election,” Mr. Paterson said. “We were very appalled at the way this election has been run.”

He said he did not blame Mr. Bruno for the problems, which did not occur in other districts, but said Mr. Spano’s campaign was “unable to control overzealous people.” There was no immediate response from Mr. Spano or the Senate Republicans.

Voters outside the Luis Munoz Marin Elementary School in Sunset Park, Brooklyn, seemed unaware of the intense jockeying between Ms. Savino and Mr. Curtis. Several people could not name the candidate they picked, explaining that they had voted based on party affiliation.

“If he was on the Conservative line, then that’s who I voted for,” said John Keegan, who evidently pulled the lever for Mr. Curtis.

“I work construction,” Steve Filchuk said. “I like Democrats. Traditionally, the Democrats support unionized workers more.”

“I used to like Bush, but I see a lot of people – a lot of my friends – they have no work now,” said another voter who supported all Democrats, Olga Martines.

There were at least some ticket-splitters, however. Anne and Daniel Perasa voted for Senator Kerry for president, but Mr. Curtis for the state Senate. They said they were impressed by his work in the community. In other elections yesterday, an assemblyman who quit earlier this year after pleading guilty to padding his expense account, Roger Green of Brooklyn, was easily reelected to the seat after facing only token opposition.

In Flushing, Democrat Jimmy Meng won a seat in the Assembly, making him the first Asian-American elected to the state Legislature.