State Treasurer SHANNON P. O’BRIEN celebrates her victory in yesterday’s Democratic gubernatorial primary.

BOSTON—State Treasurer Shannon P. O’Brien comfortably defeated three Democratic opponents in yesterday’s primary election, setting up her challenge to Republican W. Mitt Romney in the Nov. 5 general election.

The Democratic challengers conceded amiably last night and pledged to endorse her candidacy. And O’Brien, who won 33 percent of the vote, returned their sentiments after the most expensive primary season in the state’s history.

“I want to salute my Democratic opponents for all that they have done for our state,” she said.

In another key primary battle, Romney’s running mate Kerry M. Healey ’82 gained a landslide victory over conservative challenger James Rappaport.

Healey and Rappaport had been in a dead heat in recent polls, though last night she surprised pollsters by garnering 64 percent of the vote.

O’Brien finished ahead of Robert B. Reich (25 percent), Thomas F. Birmingham ’72 (24 percent) and Warren E. Tolman (18 percent).

At her victory party in Boston, mate Kerry M. Healey ’82 gained a landslide victory over conservative challenger James Rappaport.

Healey and Rappaport had been in a dead heat in recent polls, though last night she surprised pollsters by garnering 64 percent of the vote.

O’Brien finished ahead of Robert B. Reich (25 percent), Thomas F. Birmingham ’72 (24 percent) and Warren E. Tolman (18 percent).

At her victory party in Boston, O’Brien appeared assured of a victory that observers had widely predicted. Already lined up to deliver congratulations were U.S. Senators John Kerry (D-Ma.) and Edward M. Kennedy ’54-’56 (D-Ma.) and her runnning mate, Chris F. Gabrieli ’81, who handily won his primary race.

“I want to tell you something: I’m the only one in this room to run against...Mitt Romney,” Kennedy said to cheers. “And Shannon O’Brien is our next governor.”

O’Brien’s campaign manager, Dwight Robson, told The Crimson the party was stronger for having been through a competitive primary.

“The Democratic Party did not anoint a candidate,” he said. “I think Shannon O’Brien and Chris Gabrieli are better candidates for going through it and becoming battle-ready.”

He said the pair would be at commuter rail stations tomorrow morning to thanks voters for their support and rally for party unity.

But last night the nominees settled for greeting supporters in the America Ballroom of the Westin Copley Square, where two giant video screens displayed news coverage of primary night and volunteers snacked on roasted red pepper hummus.