Democrat Katherine M. Clark cruised to victory Tuesday, capturing the US House seat long held by Edward J. Markey, in a lightly contested special election.

She will become just the fifth woman to represent Massachusetts in the US House.

Turnout appeared to be very low in a race that was an anticlimactic coda to the fiercely contested seven-way Democratic primary that Clark won in October.

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A state senator from Melrose, Clark easily defeated three-little known opponents.

With 51 percent of precincts reporting, Clark had 65 percent of the vote to 33 percent for Republican Frank J. Addivinola Jr. Two independents, James Hall and James Aulenti, each had about 1 percent.

Clark could be sworn in Thursday, as the newest member of the minority party in a deeply polarized, hyper-partisan House and a Congress that will almost certainly go down as the least productive in modern history.

In Washington, she has vowed to fight “extremist Republicans” on issues such as pay equity for women and abortion rights, but will face a daunting challenge, since the GOP controls both the chamber and the agenda in the House.

Tuesday’s outcome was hardly in doubt since the district is heavily Democratic, and favored President Obama over Mitt Romney by more than 30 percentage points in 2012. Clark was also backed by her party, as well as unions and women’s groups, and raised $1.2 million.

The state and national Republican parties had all but ceded the race to Clark, giving no financial help to Addivinola, a Boston lawyer who has run for office three times and does not even live in the district. He raised just $38,000 while loaning himself nearly $62,000.