Rep. Mark Meadows (R-N.C.), has long warned about the government’s red ink, but says he will now vote for a deficit-busting budget because the GOP needs a win on tax cuts. (Ted Richardson/For The Washington Post)

House conservatives have warned for years about the threat posed by the national debt, and for months they pushed to include a path to ambitious spending cuts in budget legislation.

On Thursday, most of them plan to vote for a Senate-written budget that not only fails to make way for spending cuts but also explicitly envisions adding up to $1.5 trillion to the existing $20 trillion national debt to accommodate a tax overhaul.

GOP hard-liners have frequently been willing to oppose must-pass legislation to achieve conservative policy goals, threatening government shutdowns and federal default as leverage.

But numerous House conservatives said in interviews this week that this time is different: Republicans are under enormous pressure to pass a tax bill, given the party’s failure to take legislative action on health care, and they do not want to be seen as standing in the way.

“We’ve got to get something major done,” said Rep. Mark Meadows (R-N.C.), chairman of the House Freedom Caucus, whose members pushed earlier this year for hundreds of billions of dollars in spending cuts.

“Had we repealed and replaced Obamacare, there may not have been as much flexibility or pressure,” he added. “Am I feeling the pressure to get this done? Yes. Have I been willing to negotiate a little bit more generously because of that pressure? Yeah. That’s just shooting straight with you.”

The atmosphere of compliance emerged after President Trump called on House members to support the Senate budget language in a Sunday conference call to speed passage of the tax bill. He delivered an even blunter message on Tuesday, when he took fresh aim at Sen. Bob Corker (R-Tenn.) — one of the few Republican lawmakers who has openly warned that he would oppose a tax bill that would explode the national debt.

“Bob Corker, who helped President O give us the bad Iran Deal & couldn’t get elected dogcatcher in Tennessee, is now fighting Tax Cuts,” Trump tweeted, adding: “People like liddle’ Bob Corker have set the U.S. way back. Now we move forward!”

The upshot is that House members are set to vote Thursday on a budget resolution that includes special procedures allowing a tax bill that adds as much as $1.5 trillion to the deficit over the coming decade to pass with solely Republican votes. It does not include House language that would have mandated a tax bill that did not add much to the debt and allowed at least $200 billion in cuts to mandatory programs to pass on the same basis.

As of Tuesday, the bigger threat to passage of the budget this week appeared to be a cadre of GOP lawmakers concerned about proposals to eliminate the income tax deduction for state and local taxes. At least three lawmakers who supported the House version said they would vote against the Senate version Thursday unless a deal is reached.

Budget hawks, meanwhile, have been mostly mum.

House leaders hailed their own version of the budget when it passed earlier this month, in part by highlighting its deficit-reduction components.

“This is a budget that keeps our responsibilities to our children and our grandchildren,” Speaker Paul D. Ryan (R-Wis.) said in a floor speech. “That American legacy is seriously at risk because of our growing, deteriorating debt situation, because of our debt crisis. This budget tackles that.”

Ryan, who as House Budget Committee chairman and the GOP’s 2012 nominee for vice president routinely issued warnings about the nation’s long-term fiscal trajectory, did not mention the national debt in discussing the upcoming budget vote with reporters on Tuesday, focusing exclusively on the benefits of the tax plan.

“Adopting this budget is another sign of real momentum for tax reform, of getting the train on the tracks and getting this moving, so we can deliver real tax relief and a healthier, stronger economy for the American people,” he said.

House Budget Committee Chairman Diane Black (R-Tenn.) said Monday she was “disappointed” by the decision to jettison the effort to pursue spending cuts but also said the political demands of the moment called for it.

“The Senate really has no stomach for doing any kind of a conference committee, and obviously tax reform is very important,” she said, referring to the process for resolving differences between the two chambers. “So we’re going to move tax reform forward, and this is the way to do it.”

But it’s not only top House leaders who have stepped away from budget hawkery in recent weeks as the tax bill has come together. Self-styled fiscal sentinels such as the Freedom Caucus and the Republican Study Committee have largely held their fire on deficit-related criticism.

Leaders of both groups cited promises of future action from the White House — Meadows said he expected a push for “welfare reform” legislation next year, and Rep. Mark Walker (R-N.C.), the RSC’s chairman, said he had won a commitment for a vote on “deficit-reducing legislation.” But neither pledge comes with a clear path to becoming law.

A few hard-liners have indicated they will vote no. Freshman Rep. Matt Gaetz (R-Fla.) told reporters Tuesday that he was in no mood to “vote for a budget nobody believes in so we have a chance to pass a tax bill nobody has read.”

But those willing to go along include several members of the landmark GOP class of 2010, a group of 63 mostly stalwart conservatives who were as critical of their own party’s failure to contain the national debt as they were of Democrats.

They include Rep. Steve Womack (R-Ark.), who represents a solidly Republican northwest Arkansas district and is now a senior member of the Budget Committee. He complained in vivid terms Tuesday about having to vote for the Senate package — but confirmed he plans to support it.

“The budget that came back to us is a crap sandwich, but it happens to be the only thing on the menu,” Womack said.

The tax bill, he said, is “driving the train” and that political reality is that spending cuts will have to wait. “When I go home and people ask me about the budget, it had little to do about the budget and it had everything to do about tax reform,” he said. “It’s just as simple as that.”

Other conservatives also said their constituents are simply not as concerned about the national debt as they are about the tax legislation.

“They think the main thing is the main thing, and the main thing is tax reform,” said Rep. Bill Flores (R-Texas), a former chairman of the Republican Study Committee.

Rep. James Comer (R-Ky.), who has served in the House less than a year after a successful campaign where fiscal discipline was a centerpiece, said Tuesday he has been dismayed by the “utter disregard” from both parties for the nation’s finances.

“Having said that, this is something very important to the president. It’s something that the people in my district expect us to pass,” Comer said. “They want an accomplishment from this Congress. They want this Congress to support the president. . . . So I support the tax cuts, but I wish we would cut spending more. But, apparently, I’m in the minority.”

Damian Paletta and Dave Weigel contributed to this report.