Virginia Gov. Terry McAuliffe (Nikki Fox/AP)

Less than a week before the election, an exasperated Gov. Terry McAuliffe (D) accused a Republican in one of the state’s most competitive Senate races of lying to voters about an administration plan to address traffic on Interstate 66 inside the Beltway.

Manassas Mayor Harry J. “Hal” Parrish II is one of several GOP candidates in Northern Virginia districts airing TV ads knocking a proposal to turn a busy section of freeway into a toll road.

“He can’t talk about his record, so he’s out misleading and lying about the truth,” McAuliffe said during an appearance on WTOP. The governor used the radio show to urge voters to cast ballots Tuesday.

The proposal, to be implemented in 2017 as part of a larger I-66 expansion project, would give all drivers the option of using the highway during rush hours, when the freeway is normally limited to carpoolers and high-occupancy vehicles. Carpoolers would not have to pay the toll.

Turnout is typically low in off-year elections such as this one, but in Virginia, control of the state Senate hinges on a few races, including a contest pitting Parrish against Democrat Jeremy McPike for the seat retiring Sen. Charles J. Colgan (D-Prince William) has held for 40 years.

In addition to traffic problems in Prince William County, gun control has emerged as a major campaign issue, with former New York mayor Michael Bloomberg’s gun-control group pouring $1.5 million into the district in an effort to capitalize on a hot-button issue that could motivate Democrats who may not be paying attention to local races.

McAuliffe also accused Parrish of having a “horrible record” because of his A-minus rating from the National Rifle Association, opposition to Medicaid expansion and casting of a tie-breaking vote allowing Manassas to impose hospital­-style restrictions on abortion clinics. The state Board of Health recently reversed a similar set of regulations for existing clinics, which put Virginia at the center of a national debate during former Republican governor Robert F. McDonnell’s term.

In a recent ad, Parrish stands along the busy highway and says: “Elect me, and we’ll put a stop sign on any new toll on a road that you already pay for.”

Asked to respond to the ad, McAuliffe delivered a five-minute tirade against Parrish and Republicans and said the “only potential new toll is for a single driver who is prohibited inside the Beltway during rush hour.” He added: “Is that clear enough for you?”

Democratic candidates, including McPike, have increasingly backed away from the plan, although McAuliffe noted several chambers of commerce favor it.

Speaker William J. Howell (R-Stafford), who held a news conference on the issue this month in a Fairfax County park overlooking I-66, said in a statement Wednesday that the optional toll rates are too costly for working-class families.

“I’m disappointed by the governor’s tone and the personal attacks he levied today,” he said. “That may be the norm in Washington, D.C., but it simply isn’t productive.”

The tolling system is meant to deal with single drivers who evade carpool regulations on I-66 that require vehicles traveling on the road inside Interstate 495 during rush hours to have at least two people.

Under the plan, those drivers would be charged a maximum of $17 if they travel on the 10-mile stretch of highway during peak morning and afternoon travel times, while carpoolers would be allowed to pass through without paying.

Initially, the plan would have cost reverse commuters $3, but McAuliffe said Wednesday that they will not be charged. McAuliffe spokesman Brian Coy said the plan was changed as a result of public comment.

The toll revenue would go toward improving nearby ancillary roads and expanding I-66 inside the Beltway when it is clear that there are no other solutions to easing traffic on the narrow highway, Virginia Transportation Secretary Aubrey L. Layne Jr. has said.