New Haven Mayor John DeStefano Jr. squeaked past Stamford Mayor Dan Malloy to become the Democratic gubernatorial nominee Tuesday night in a race too close to call until almost 90 percent of the vote was reported.

Another New Haven native took a dive in the primary election, as Senator Joseph Lieberman ’64 LAW ’67 lost to challenger Ned Lamont SOM ’80, who began his campaign just eight months ago as an unknown Greenwich businessman. Lieberman announced, while conceding the primary, that he would run as an independent candidate in November.

Election turnout set a new record for a statewide primary, as more than 43 percent of the state’s 700,000 registered Democrats cast ballots. DeStefano defeated Malloy by just 1 percent, while Lamont defeated Lieberman by a margin of 4 percent, according to preliminary results.

According to the Secretary of State’s Office, nearly 7,000 voters switched their party registration from unaffiliated to Democratic in the last three months, presumably to vote in the highly contested primaries. The majority of Connecticut’s eligible voters are registered as unaffiliated.

Tuesday evening, DeStefano, introduced by the U2 song “Beautiful Day,” spoke of his commitment to establishing universal healthcare, a new economic development program, and a reformed property tax system. Calling Connecticut the “smartest, brightest, hardest-working state,” DeStefano also thanked the unions, particularly Service Employees International Union 1199. which deployed approximately 350 union members during voting hours, according to a local union leader.

“Working families of this state should see state government … as a partner,” DeStefano said. “We’re all going to come together not around a party so much as around a set of values.”

The persistently close tally — which began with Malloy maintaining a slight lead — as well as the need to time speeches from four politicians around the state, delayed DeStefano’s victory speech until nearly midnight, making him the last of the major candidates to speak.

Earlier in the evening, DeStefano supporters had booed at Lieberman’s concession speech when he indicated that he would file Wednesday the papers necessary to run as a third-party candidate. Although a number of DeStefano supporters began the evening wearing Lieberman t-shirts, as New Haven is the Senator’s hometown, few such shirts were visible after Lieberman’s speech.

DeStefano and Malloy, both of whom spoke after Lieberman’s concession speech, made pointed references to the need for party unity in the November race. DeStefano will now face the challenge of campaigning against incumbent Republican Governor M. Jodi Rell, who had a 74 percent approval rating as of July 20.

“It is incumbent upon us as Democrats to rally together to make sure a Democrat is elected,” Malloy said. “Connecticut needs new leadership … If John DeStefano is to lead us to that change, you can be assured I will be working with him.”

The impact of Lieberman’s independent candidacy remains to be seen for n both New Haven and Yale. Board of Alderman President Carl Goldfield said reactions from his constituents and colleagues are varied, though he said most people cast the senator’s decisions in moral terms, either praising him for his personal integrity or condemning him for betraying his party.

Yale College Democrats President Brendan Gants ’08 said he was disappointed by Lieberman’s decision, which he said could split Democrats. The Yale Democrats have not yet decided how to confront the potential divide in its membership, he said.

“People are going to have all kinds of different feelings about this race,” Gants said. “It really remains to be seen how that race is going to shape up, but we’re definitely excited to return a Democratic senator to Congress in the fall.”

In an odd turn for the gubernatorial race, Malloy’s candidate for lieutenant governor, Mary Glassman, defeated DeStefano’s candidate, Scott Slifka. The November ticket for governor will therefore be DeStefano/Glassman, even though until Tuesday night the two were opponents.

–Staff Reporter Andrew Mangino contributed to this report.