The leader of the most prominent super PAC charged with electing Republicans to the House next year delivered a blunt warning to GOP lawmakers ahead of Thursday’s House vote on a $1.5 trillion tax bill: If you want our help, you had best vote for this bill.

Corry Bliss, who runs the Congressional Leadership Fund, which has close ties to House Speaker Paul D. Ryan (R-Wis.) and high-dollar GOP donors, said in an interview that Republicans who vote against the Tax Cuts and Jobs Act on Thursday should not assume they would have the group’s support going into a grueling midterm election year.

“CLF will never spend a dollar attacking a Republican,” Bliss said. “But CLF is going to raise and spend $100 million to protect the Republican majority. CLF, like any organization, will allocate resources to friends and family first.”

CLF has played hardball ahead of a key House vote before. After Rep. David Young (R-Iowa), who represents a swing district, announced plans to oppose the Republican health-care bill in March, the group canceled plans to open a field office to support Young in his district. Although Young later voted to advance the bill, CLF has not moved to reopen the office or otherwise assist him.

Bliss said he wants to “ensure tax reform passes the House with momentum,” and the group’s ultimatum could weigh on the minds of Republicans representing swing suburban districts — especially those representing relatively high-cost-of-living areas where the GOP decision to scale back the deductions for mortgage interest and state and local taxes could lead to higher tax bills.

The CLF is engaged in 13 races in which a Republican is the incumbent. Three of them have not announced positions on the tax bill: Steve Knight and Edward R. Royce, both of California, and Barbara Comstock (Va.).

Comstock has been under special pressure since Republicans suffered major losses in state-level elections in her district last week. She previously voted against the Republican health-care bill after being pressed by her constituents — even after CLF ran ads urging voters to thank Comstock for supporting the bill. CLF did not abandon support for Comstock after that debacle.

Bliss said the lesson of Virginia for Republicans should not be to become more timid on key GOP priorities.

“The elections in Virginia crystallized how important it is to cut middle-class taxes,” he said. “The choice before us as a party is very simple: cut middle-class taxes or else.”

The American Action Network, a related organization also headed by Bliss and affiliated with Republican establishment donors, has spent $20 million to promote the middle-class benefits of the GOP tax bill. Bliss said the group is “prepared to spend at least an additional $5 million over the next 30 days.” That would double the $12 million the group spent on the health-care fight.

“We wanted to start messaging on tax reform early, and we wanted to help conservative groups work together,” he said. “We thought it was very important to be aggressive during August when members would be home in their districts, and AAN spent over $5 million during that month.”

The group also held “Tax Reform Friends and Allies” meetings since the summer, hosting representatives from more than 50 conservative groups, as well as Ryan, Sen. Rob Portman (R-Ohio), representatives from the Trump administration, and other members of the House and Senate leadership and key committees.

Bliss said he is not impressed with the Democratic messaging against the bill, which has pointed out that corporations and wealthy Americans would receive more than 80 percent of the overall tax cut in the House bill.

“There’s a real danger if Democrats are seen as working against tax reform,” he said.

“If Democrats are working to kill the plan simply because it’s the Republican plan or the president’s plan, they will pay a big political price,” he said, pointing to a swing Nebraska district when CLF is heavily engaged: “They can yell and scream, ‘Rich people! Corporate tax cuts!’ But, if a middle-class voter in Don Bacon’s district gets an extra $1,200 for their family next year, who are they going to vote for? The Republican or the Democrat? They’re going to vote for the Republican.”