Health-insurance plans of as many as 250,000 Virginians will be canceled in January because the policies do not meet the standards set by the Affordable Care Act, a development that Republican Ed Gillespie hopes will boost his prospects as he tries to unseat Sen. Mark R. Warner.

The high number of potential cancellations, predicted this week at a meeting of the Virginia Health Insurance Reform Commission, instantly became fodder in the Senate race. Gillespie has made Warner’s support for the ACA the central theme in his uphill battle against the incumbent Democrat, a former governor who had a 22-point lead over the Republican in a recent poll.

Gillespie, a former Republican National Committee chairman and lobbyist, rolled out a series of statements, headlining one of them “250,000 broken promises.” His campaign also touted the number as it unveiled a TV ad with video of Warner promising in 2009 that he would not support a health-care law that takes away policies that people already had and liked.

“Because Mark Warner worked to pass Obamacare, 250,000 Virginians are losing the health insurance they liked, with thousands getting hit with huge out-of-pocket cost increases while unable to see the doctors they trust,” Gillespie said in a prepared statement.

Warner’s campaign shot back by highlighting some of the law’s more popular components and repeating the senator’s vow to fix any of its flaws.

“Just weeks from election day, Gillespie still has not said how he would fix health care. Instead he would take us back to the days when families were denied health care because of pre-existing conditions and women were charged more than men for the same coverage,” Warner campaign spokesman David Turner said in a written statement.

Republicans were poised to keep the issue on the front burner in Richmond next week as the General Assembly meets for a special session on whether to expand Medicaid under the ACA.

A Democratic legislator, meanwhile, was finalizing legislation Friday that he hoped could be introduced during the special session. State Sen. George L. Barker (D-Fairfax) planned to propose a bill that would give Virginians more time to adjust to the new ACA standards.

The federal health-care law that took effect in January established certain minimum requirements for insurance policies, and plans that fell below those standards were supposed to be eliminated. An estimated 250,000 people in Virginia got a one-year reprieve by renewing those noncompliant policies late last year, but now those plans are set to expire by the end of the year.

After the new law caused a flurry of cancellation notices across the country late last year, the Obama administration issued reprieves. The deadline to comply with the standards has been extended into 2017. But Virginia law has prevented insurers in the state from extending the reprieve past this year.

Warner spokesman Kevin Hall said the senator has pressed federal and state officials to allow for those extensions and supports changing state law for that purpose in the coming special session.

“Federal policy allows states to continue to give consumers the option of keeping their existing plans, so this is now a state issue,” Hall said. “The Virginia legislature will have an opportunity in next week’s special session to allow the state insurance commissioner to give consumers the option of keeping their current plans. Thirty-seven states, including North Carolina, have already done that, and the Virginia General Assembly can and should do the same.”

The health plans in question are those purchased by individuals, typically people who are unemployed or do not have insurance through their jobs. The precise number of Virginians whose plans are expected to be eliminated is not known, but roughly 250,000 of the 400,000 Virginians in the individual market opted to stick with their old plans last year.

Doug Gray, executive director of the Virginia Association of Health Plans, testified before the commission and said the number is just an estimate. Some of those people might have looked at their options in the intervening year and discovered that there are better plans available or that they are eligible for federal subsidies.

“Everybody wants a number, and we don’t have one. That’s the truth,” he said. “They’re trying to guess, and when politics shows up, some people are guessing high.”

Del. Kathy J. Byron (R-Bedford), the commission chairwoman, and Sen. Frank W. Wagner (R-Virginia Beach) touted the number as evidence that the ACA is deeply flawed.

“This law is causing untold heartache and genuine hardships for thousands of Virginians,” Byron said in a written statement. “It is becoming increasingly clear that the best option would be to repeal this poorly crafted law and start over.”