Stephen F. Lynch, the longtime Congressman from South Boston, launched his run for Senate Thursday. In his remarks, Lynch, a Harvard Kennedy School graduate, spoke of a campaign that will rely on a strong grassroots ground game inspired by Harvard Law School professor Elizabeth Warren’s campaign in her hard-fought victory over incumbent Scott Brown.

“We won’t win this race because of money or endorsements or backdoor deals to clear the field,” Lynch told a crowd of more than 300, assembled in the event room at the Ironworkers Local 7 headquarters in South Boston. “We will win by earning the support of the people of this great state by the way it should be won: by courage, by honesty, and by hard work.”

Lynch enters the race as the clear underdog. His opponent, Representative Edward J. Markey of Malden, not only leads in the polls but has also been endorsed by the Democratic Senatorial Campaign Committee and by Secretary of State John F. Kerry, who on Friday will vacate the seat now being contested.

Additionally, Markey holds about a four-to-one advantage in cash on hand, according to campaign finance reports.

But Lynch, who worked as an ironworker for 18 years before entering public service in 1996, embraced his status as a party crasher. Channeling Warren, he said that he was happy not to be a part of the Washington establishment in response to opponents who suggested that he would not fit in with the Senate.

“After I thought about it for a few minutes,” Lynch said, pausing for the punchline, “I had to agree, because it’s true. I will not fit in in the United States Senate, but neither would you.”

The crowd, largely composed of card-carrying union members, erupted in raucous applause.

Throughout the event, the Warren inspiration was clear, if subtle. In the office where Lynch paced before he entered the event room, a “WARREN FOR SENATE” sign was taped to the window.

And before Lynch took the stage, Paul F. Lynch, business manager of Ironworkers Local 7, reminded the crowd of the potential of an organized ground game.

“We can do this,” he told them. “We proved it when we put Elizabeth Warren in as a senator. We can do it again.”

After his speech, Lynch was asked if he would target younger voters as Warren did with great success.

“I want everyone,” he said, adding that college campuses would be a priority. “We’ve got to motivate the younger base.”

Seconds later, Lynch shook hands with yet another supporter who offered “anything you need, anything I can do to help.”

Relying on his supporters’ enthusiasm, Lynch was cautiously optimistic. When asked if he thought the loyal supporters from his district could reach voters across the state, Lynch responded positively.

“Yeah, I think so,” he said. “I don’t have the big money, I don’t have the big endorsements. All I got is people.”

—Staff writer Matthew Q. Clarida can be reached clarida@college.harvard.edu.

This article has been revised to reflect the following correction:

CORRECTION: Feb. 2, 2013

An earlier version of this article incorrectly identified Paul F. Lynch, the business manager of union chapter Ironworkers Local 7, as the brother of Congressman Stephen F. Lynch. In fact, the two men are not related.