Democrats retained their overwhelming majority in the state Legislature Tuesday, with incumbents winning nearly every contested race and Democratic challengers picking off some of the state’s few Republican seats.
Senate President Therese Murray, a Plymouth Democrat, fended off a challenge by a Republican who nearly beat her two years ago.
“This is a big red district and I’m the only Democrat ever elected here,” said Murray, who defeated her opponent, Thomas F. Keyes, by a wide margin. Two years ago, Keyes won nearly half of the vote. “Republicans and unenrolleds came out and voted for me. It makes me feel that people appreciate the job I’m doing and I appreciate their vote.”
Democrats also won the races to succeed three Democratic senators who decided not to seek reelection: Steven Baddour of Methuen, Frederick E. Berry of Peabody, and Susan Fargo of Lincoln.
Robert Hedlund of Weymouth, the only Republican senator to face an opponent, was well ahead in early returns.
In Fargo’s former district, former Democratic state senator Michael J. Barrett of Lexington made a political comeback, claiming victory before 9 p.m. According to his campaign, he beat Chelmsford Republican Sandi Martinez by a wide margin.
“I feel the work ethic kicking in. It’s not elation, it’s kind of a sober sense of responsibility,” he said. “I’ve got to deliver, the state has to deliver — the problems seem huge, some of the environmental issues, some of the job creation challenges seem enormous. I’m not going to be celebrating, I’m going to be thinking.”
Democrat Joan B. Lovely of Salem declared victory a little after 9 p.m. based on results that showed her beating Richard A. Jolitz, a Republican from Beverly, by a wide margin in the race for the seat held by Berry, the Senate majority leader, for 30 years.
It was the first open seat in decades in the district made up of Beverly, Danvers, Peabody, Salem, and Topsfield.
“I feel elated. I’m absolutely so grateful for all the support,” she said.
The most heavily contested Senate race was in the Merrimack Valley, where Kathleen O’Connor Ives, a Democratic Newburyport city councilor, defeated three candidates to succeed Baddour, who resigned in April to become a partner of a private law firm.
Ives beat Shaun A. Toohey, a Republican Haverhill School Committee member, and unenrolled candidates James Kelcourse and Paul A. Magliocchetti.
Of 200 legislative seats, 75 were contested. Twelve seats were vacant — the officeholders either left, ran for another office, or withdrew. One new district was created in last year’s redistricting for residents of Lawrence and Andover.
Several races were rematches between bitter rivals including two House races where incumbents were facing challenges from the candidates they defeated two years ago.
Democrats, hoping that high turnout would translate into victory in the legislative seats, targeted several Republicans, including some who were swept into office in 2010 in a wave of voter dissatisfaction.
In Marlborough, former state representative Danielle W. Gregoire beat freshman Republican Representative Steven L. Levy, who defeated her two years ago.
“It feels awesome. I couldn’t have done it without all the help I got,” said Gregoire. “It hasn’t sunk in yet. It’s amazing.”
In Andover, Republican Representative James Lyons fought back a challenge from Barbara L’Italien, the woman he unseated in 2010. L’Italien, a Democrat, served in the House for eight years before her defeat in 2010.
Democratic newcomer Jonathan Zlotnick, who graduated from the University of Massachusetts Lowell in May, beat freshman Republican Representative Richard Bastien of Gardner.
In Duxbury, Democrat Democrat Josh S. Cutler of Duxbury beat Republican Karen E. Barry in the race to succeed Daniel K. Webster — to become the first Democrat ever to represent the district.
Webster, a five-term Republican incumbent, withdrew from the race in September amid allegations by the state board that regulates lawyers that he misused client funds.
Barry, a local GOP activist, jumped in the race with only a few weeks left.
Democrat Paul Heroux, a public policy consultant with several degrees including one from Harvard’s Kennedy School of Government, ousted incumbent Republican George Ross from Attleboro.
Republicans picked up at least one House seat previously held by a Democrat. Leonard Mirra, of West Newbury, beat Democrat Barry Fogel, also of West Newbury, in the race for the seat held by Harriet Stanley, who did not seek reelection.
Globe correspondents John Laidler, Ellen Ishkanian, Calvin Hennick, Ryan Mooney, and Laura E. Franzini contributed to this report. Andrea Estes can be reached at email@example.com.