After an arduous and contentious campaign, New Haven voters will go to the polls today to cast ballots in the city’s most competitive — and costly — Democratic mayoral primary in a decade.

The bitter battle between the four-term incumbent Mayor John DeStefano Jr. and the 21-year state legislature veteran Sen. Martin Looney has divided New Haven’s dominant Democratic Party like no election in recent memory. The $452,000 raised for the mayor’s re-election fund is higher than any other campaign in New Haven history. And throughout the city, neighbors have campaigned against neighbors and former allies have stared at each other across a widening political gulf.

The winner in today’s primary will earn both the right to take on Republican candidate Joel Schiavone ’58 in November’s general election and the backing of New Haven’s Democratic machine.

Today, supporters of each candidate will call voters and drive them to polling places, which will be open from 6 a.m. to 8 p.m.

Voters are also deciding which aldermanic candidates will progress to the general election in November in 12 contested primaries, which include wards 2 and 22, near the Yale campus. The split in the Democratic party has brought special attention to these elections, with most of those races pitting Looney and DeStefano supporters against each other.

In Ward 22, which includes Ezra Stiles and Morse colleges, incumbent Grace Gibbs, a Looney supporter, takes on Mae Ola Riddick, a DeStefano backer and former alderwoman who Gibbs defeated four years ago.

In the other 18 wards, unopposed candidates, including Ben Healey ’04 in Ward 1 and Dolores Colon ’91 in Ward 7, will automatically advance to November’s general election without appearing on today’s ballot.

And Monday, both DeStefano and Looney were preparing for the day ahead, working to the last minute to secure votes. Looney spent the day calling voters who had not been contacted previously and those who were undecided, making a personal pitch for a changing of the City Hall guard.

The challenger also toured his four campaign headquarters, meeting with staff and volunteers late into the evening.

“I believe strongly that I am going to win,” Looney said in a phone interview. “After eight years, I believe the people do want a change, and that message has resonated.”

DeStefano appeared at several functions Monday, capped off by a visit to the Bella Vista senior home, a traditional election eve stop for the mayor.

A crowd of nearly 200 of the complex’s residents packed into a large room, dancing the “Electric Slide” and singing along as DeStefano worked the room.

“Look at where we started eight years ago,” DeStefano told the crowd in a brief speech. “I think I’ve done a pretty good job.”

DeStefano’s campaign has raised more funds than any mayoral campaign in city history, said his manager, Julio Gonzalez ’99.

DeStefano also repeated his frequent accusation that Looney engaged in negative campaigning, telling the audience his opponent has been “calling names.”

Looney vigorously denied the charges, saying he thought the campaign had been based on “issues and documented facts.”

Both sides agreed that field organization will be important throughout the day, a point Looney emphasized.

“We need to generate turnout, contact and identify favorable voters, and maximize turnout in areas with a strong potential vote,” he said.

Voters today will also nominate a Democratic candidate for city clerk, who will vie for the spot of the outgoing Stanley Rogers. DeStefano is backing Ron Smith, while Looney supports Katurah Abdul-Salaam.

Tonight, the DeStefano campaign will host a party at Alchemy, located at College and Crown streets. Looney supporters will gather at Tycoon’s at Orange and George streets.