Emerging from a primary campaign that lacked the intensity many anticipated, U.S. Rep. Edward Markey held off delegation mate Rep. Stephen Lynch in Tuesday's Democratic primary for U.S. Senate, moving on to face former Navy SEAL and political upstart Gabriel Gomez in a late June special election that will pit a 36-year-veteran of Congress against a political newcomer.

Markey and Gomez are vying for the U.S. Senate seat held for 28 years by Secretary of State John Kerry before he accepted the State Department job from President Obama in January.

Markey did not mention Gomez by name during his victory speech at the Omni Parker House in downtown Boston, but later assailed the new face of the GOP for refusing, as former Sen. Scott Brown did, to sign a pledge banning what Markey called a "tsunami of polluted political money" that will flood Massachusetts from conservative billionaires like the Koch brothers and Super PACs led by Karl Rove and others.

"They are ready to move mountains of money to buy this election," Markey said, calling on Gomez again to sign the so-called "People's Pledge."

Markey, 66, defeated Lynch, 58, with 57 percent of the vote to Lynch's 42 percent, applauding the former ironworker from South Boston at a victory rally in downtown Boston as his "brother in the Democratic party."

"My father was a milkman. Every day he got up and delivered the goods. And in the United States Senate, I'm going to deliver results," Markey told his supporters, ticking off his support and fights in Congress for gun control, clean water, safe ports and affordable health care.

In Gomez, Markey will be up against a socially moderate Republican with Colombian roots and a military and business background. Gomez supports gay marriage, term limits and fiscal restraint. "The fight begins tonight to ensure the Republicans do not win this seat," Markey said.

Former Gov. Michael Dukakis predicted that the next seven weeks would be "very tough" and won "on the streets" by reaching out to voters.

Dukakis said Gomez's newcomer status could be an advantage for the Republican, especially in light of the difficulties presented by a shortened special election timetable in conveying a message and defining an opponent.

"I have no idea who he is or where he stands, and in way that can be an advantage," Dukakis said.

Thomas O'Neill III, a public relations consultant and former lieutenant governor of Massachusetts, said Democrats were still trying to "figure out" Gomez. "Democrats don't know him, and he hasn't defined himself," O'Neill told the News Service.

State Sen. Karen Spilka, an Ashland Democrat who is weighing a run for Markey's seat should he win, said Markey's experience in Congress should be viewed by Democrats as a positive. "At a time like this, I think we can use someone who can hit the ground running, not someone who needs two or three years to come up to speed," Spilka said, previewing a potential line of attack on Gomez as inexperienced in politics.

Markey advisers suggested some of first knocks against Gomez would be on guns, abortion and entitlement programs, calling the Republican nominee an opponent of bans on assault weapons and high capacity magazines and someone who can't be counted upon to protect Social Security and Medicaid or a woman's right to choose.

"We need to make the NRA stand for Not Relevant Anymore. I want these guns off our streets," Markey said.

Overshadowed in the weeks leading up to the primary by the Boston Marathon bombings, candidates on both sides of the race largely failed to generate a wellspring of interest from voters coming down from a lengthy, grueling U.S. Senate race in 2012 between Sen. Elizabeth Warren and Scott Brown.

Turnout was low across the state, propped up in places like South Boston where there was also a special election for state Senate and in the more than 80 municipalities that scheduled local elections to piggyback off the Senate primaries.

A stalwart liberal Democrat from Malden, Markey has represented the suburbs north and west of Boston in Congress for the past 36 years and he campaigned on many of the causes that have been central to his political career for a generation, emphasizing his support for abortion rights, environmental protection, gun control and Obama's landmark health care law that Lynch voted against.

From the start of the race, Markey emerged as the clear favorite of the Democratic establishment, racking up early endorsements and nods of support from Kerry and national Democrats.

Lynch, however, embraced the role of underdog, waging a campaign focused on appealing to working-class voters like those he grew up with in South Boston as a union leader and ironworker. Elected to Congress in a special election held on Sept. 11, 2001, the more socially conservative Lynch relied on his union roots to appeal to middle class voters as he tried to paint Markey as a Beltway insider.

Even as polls and conventional wisdom predicted a Markey victory from the outset, Lynch insisted up until his final rally on Monday night that he would prevail.

The campaign between the two long-time colleagues lacked a degree of bite, but Lynch did amplify his attacks on Markey in the first debate after the terror attack in Boston, accusing Markey of not adequately supporting homeland security.

Markey focused his criticism of Lynch on the South Boston Democrat's vote against the Affordable Care Act. Lynch was the only member of the Massachusetts Congressional delegation to oppose the bill, a vote Markey called a mistake and one that ran counter to the ideals of expanding access to affordable health care championed by the late Sen. Edward Kennedy.

George Bachrach, a former state senator who ran Markey's first campaign for Congress in 1976, said, "I don't think anyone can accuse him of jumping in line or not waiting his turn, but I don't think I've ever seen anyone more prepared to do this job."

Citing Markey's fights in Congress against the National Rifle Association, British Petroleum after the gulf oil spill and his support of clean energy, Bachrach dismissed criticism that Markey had been handpicked and propelled by national Democratic interests.

"He earned it. His support tonight will not come from Washington. It will come from being on the right side of issues like women's rights and health care," Bachrach said.

Democrats plan a "unity breakfast" at the Omni Parker House in downtown Boston for Wednesday morning to rally behind Markey as the party's candidate for U.S. Senate. Gov. Deval Patrick and other officials plan to attend.