During a generally sleepy candidates’ forum, the crowd in the McLean Community Center started out small as opponents in various Virginia House elections traded ideas on easing traffic or attracting more jobs to the area.

Then came the debate for the hotly contested 34th District seat and, like a main-event boxing match, a suddenly full house was electrified by the competitors’ clear dislike for each other.

Republican Del. Barbara J. Comstock and Democrat Kathleen Murphy are locked in a fierce battle for Comstock’s seat amid what appears to be a Democratic surge in Northern Virginia. A recent Washington Post/Abt SRBI poll showed likely voters leaning toward Democrats in the races for governor and lieutenant governor, while the race for attorney general appears unusually close.

A dozen House races are considered competitive, and the well-heeled 34th District, which was evenly split during the 2012 presidential election, is on the radar of both major parties.

Comstock, 54, has raised nearly $1 million in her bid for a third term, according to the Virginia Public Access Project’s Web site. Murphy, 65, a former international trade adviser with the Department of Commerce, has raised nearly $400,000.

Barbara J. Comstock, R-Fairfax. (Bob Brown)

The candidates have attacked each other with increasing vitriol in a war of news releases and e-mails that escalated this month when Comstock abruptly backed out of a Great Falls debate at which gun-control activists supporting Murphy were expected to demonstrate.

Each side accuses the other of lies and blatant distortions.

Comstock complains that Murphy is offering voters a false picture of her voting record, particularly on gun control and traffic congestion. On guns, Comstock emphasizes her support for cracking down on straw purchasers and for better mental health screening in connection with firearm sales.

On transportation, she said, “I’m a go-to delegate,” despite having voted against landmark transportation legislation that will fund road improvements across the state. She said she is working tirelessly to identify projects that need funding in the traffic-plagued district, which hugs the Potomac River and includes parts of Fairfax and Loudoun counties.

Comstock, in turn, has accused Murphy of not paying taxes, calling her in one news release “the Leona Helmsley of Virginia,” a reference to a famous businesswoman convicted of tax evasion in the 1980s.

Murphy said taxes were paid late on property her husband owns in Colorado and on a condominium building they own together in McLean. Her campaign provided documents that she said show the Colorado property is now in good standing, and public records show no tax liens against Murphy or her husband in Virginia. Murphy acknowledged that taxes are owed on a home in New York occupied by her ex-husband, but she said, “I have no control over that.”

Murphy also took issue with Comstock’s portrayal of her as a negligent voter in past elections, an allegation she said was based on poor record keeping at the Fairfax County registrar’s office. Public records show that Murphy has voted in every election since 1997.

Virginia general election

Hear from the candidates in the three statewide races and dozens of House of Delegates races.

“They’re all a distortion,” she said of Comstock’s remarks, accusing the incumbent of avoiding policy issues. “She would rather exaggerate stories about me so that I look bad.”

The candidates’ mutual disdain was evident in the icy greeting they offered each other while the auditorium seats filled with what became a disruptive crowd of supporters from each side.

Several times, moderator Peggy Fox asked the audience, “Please, don’t do the hissing noise,” and she appealed to them, “Let’s everyone be an adult” as the candidates responded to questions about gun control, women’s health issues and ethics in state politics.

“Unlike my opponent, I would not vote for transvaginal ultrasounds, especially not for rape victims,” Murphy said at one point, referring to a proposal that would have required women considering an abortion to undergo the invasive procedure. Comstock guffawed and said Murphy distorted her record on women’s health issues. Then she accused Murphy of being against birth control because she had taken a stand against over-the-counter sales.

Both candidates say they would work to bring more jobs to the district, but Comstock has been endorsed by the Northern Virginia Technology Council’s TechPAC and several other business groups. Murphy, who owns a legislative consulting company, said she would like to foster the development of more technology companies in the 34th District.

On crime, Murphy has highlighted the 1998 shooting death of a brother, Steve Johnson, during a robbery as the chief reason she supports stricter gun control.

Comstock has emphasized her years of fighting human trafficking, including pushing through several pieces of legislation to crack down on prostitution rings.

The candidates said they have worked late into the night to secure votes in what leaders in their parties have said will be a down-to-the-wire election.

“This isn’t an easy thing to do,” Murphy said at the McLean debate. “It’s not fun sometimes.”