WASHINGTON: Donald Trump faces a reckoning Thursday as US lawmakers vote on his presidency’s biggest legislative test, the Republican plan to repeal and replace Obamacare, as conservatives vowed to kill it unless important last-minute changes are made. The Republican-controlled House of Representatives votes on the controversial measure despite challenges over whether Trump and ally House Speaker Paul Ryan have enough backing to get the measure over the finish line. With Democrats opposed to Trump’s effort to rip out his predecessor’s crowning domestic policy achievement, and his own party’s right flank in revolt, Trump brought in wavering lawmakers Wednesday to try to tip the scales in his favor. “Big day for healthcare. Working hard!” Trump tweeted. Insiders say Trump’s meetings have been focused less on specifics than on the politics of “Trumpcare” failing — an outcome that would be a humiliating defeat for the billionaire leader at the start of his term. But some lawmakers have emerged defiant, including Mark Meadows, chairman of the grassroots conservative Freedom Caucus. “We need changes to the underlying bill before we vote on it in the House,” Meadows told reporters. “There’s not enough votes to pass it tomorrow.” Speaking on Fox News later Wednesday Meadows said that “to say that we’ve got a deal — that wouldn’t be accurate,” but did say that he and Trump had come to “an agreement in principle.” “There’s still work to be done but I can tell you that the president is engaged.” For years, Republicans have promised to overturn Obama’s reform, describing it as government overreach. But some lawmakers have balked at their own party’s plan, saying it is still too costly for the government. Others worry that their constituents will no longer be able to afford health insurance. A nonpartisan congressional budget estimate says 14 million Americans would lose their coverage from next year under the Republican plan. “We’ll see what happens,” Trump said Wednesday during a meeting on health care and women. The House vote on the American Health Care Act (AHCA) looks tight. The Democratic minority is prepared to vote against it as a bloc, so Republican leaders need to limit defections to about 22 out of their party’s 237 representatives — depending on how many members end up casting a vote. Those who are the most unhappy with “Trumpcare” are members of the Freedom Caucus — heirs apparent to the ultra-conservative Tea Party movement. They call the new bill — championed by Ryan — “Obamacare Light,” as it will only reduce, not eliminate, health coverage subsidies by replacing them with refundable tax credits. Party leaders made tweaks to the bill late Monday, which they hope will allay concerns enough for the bill to squeak by in Thursday’s vote. The White House was all in. “There is no plan B,” White House spokesman Sean Spicer said Wednesday. As the vote neared, the arm-twisting on Capitol Hill and at the White House continued. Ryan could decide to postpone the vote if it becomes clear the measure will fail. Several conservatives want to see the bill lift burdensome regulations on insurance companies — including requirements for preventive care — that they blame for the rise in insurance premiums. As Meadows stood firm, Ryan countered: “We’re not losing votes, we’re adding votes, and we feel like we’re getting really, really close,” the speaker said. On Tuesday, House Republican and Trump loyalist Chris Collins said some of the 20 to 30 lawmakers still in the “no” camp could vote “yes” at the last minute to spare the party a major setback. New York Republicans like Collins have won a concession on taxes for their constituents, and have since shifted to “yes.” Trump has put his own credibility and deal-making skills on the line for the measure.