By Susan Cornwell and Yasmeen Abutaleb
WASHINGTON (Reuters) - U.S. President Donald Trump warned Republican lawmakers on Tuesday that voters could punish them if they do not approve a plan he favors to dismantle Obamacare, as pressure grew on the businessman-turned-politician to win the first major legislative battle of his presidency.
In one of the few visits he has made to the U.S. Capitol since taking office two months ago, Trump told fellow Republicans in the House of Representatives they would face "political problems" for opposing the bill that takes apart Obamacare and partially replaces it.
"The president was really clear: He laid it on the line for everybody," House Speaker Paul Ryan, the leading proponent of the bill, told reporters. "We made a promise. Now is our time to keep that promise. ... If we don't keep our promise, it will be very hard to manage this."
While Republicans control both the House and Senate, the party's leaders face a difficult task in uniting their members behind the healthcare bill, just the first in a series of reforms that Trump has promised, including overhauls of the tax system and business regulations.
Wall Street fell sharply on Tuesday as investors worried that Trump may struggle to deliver on his promise of tax cuts, which has propelled the market to record highs in recent months.
The S&P 500 and Dow Jones Industrial Average lost over 1 percent in their worst one-day performances since before Trump's election victory on Nov. 8. The S&P financial index sank 2.87 percent, its biggest daily fall since June.
“You have this back and forth in Congress with the new healthcare plan and you have this belief that if the healthcare plan can’t pass, then they can’t move on to taxes. There’s this feeling that if things don’t get done, then maybe what the market has been anticipating gets held up," said Mark Kepner, managing director at Themis Trading in Chatham, New Jersey.
Some conservative lawmakers believe the healthcare bill does not go far enough, while moderate Republicans worry that millions of Americans will be hurt by the dismantling of the 2010 Affordable Care Act, Democratic former President Barack Obama's signature healthcare legislation.
Party leaders hope to move the bill to the House floor for debate as early as Thursday. But the administration and House leadership can afford to lose only about 20 votes from Republican ranks or risk the bill failing since Democrats are united against it.
Republican Congressman Mark Meadows, chairman of the conservative House Freedom Caucus, said the caucus has decided not to vote as a bloc on the bill, meaning Republican leadership could still win votes from some of the group's roughly three dozen members
In a tweet, CNBC business news channel listed 26 House Republicans who have said they cannot support the measure.
Repealing and replacing Obamacare was one of Trump's main campaign promises and has been a goal of Republicans since it was enacted.
Republican Representative Walter Jones said Trump told lawmakers in the closed-door meeting at the Capitol that if the Republican bill does not pass, they would face "political problems." Jones said he thought Trump meant lawmakers could lose their seats.
While Trump predicted that Republicans could face challenges in primary contests ahead of the 2018 midterm elections if they do not gut Obamacare, there is also danger to them in doing so. If the Republican bill is passed, millions of voters might lose their healthcare coverage.
The Congressional Budget Office said last week that 14 million people would forfeit coverage under the House bill over the next year, although that number could change based on the most current version of the legislation.
Nancy Nielsen, associate dean for health policy at the University at Buffalo's Jacobs School of Medicine, said Republican leaders were in a tough spot.
"It is a not-so-delicate balancing act, as they have to win over the most conservative House and Senate members without causing an outrageous backlash from voters now or in the next election," Nielsen said.
Democrats oppose the Republicans' plan, saying it would hurt the elderly, poor and working families while giving tax cuts to the wealthy.
Republican leaders tweaked the bill this week to try to satisfy critics, mainly from their own party.
Republican chairmen for two key committees said late Monday they proposed more funding for tax credits, which conservatives have opposed, that would give the Senate flexibility to help older people afford health insurance. Additionally, Obamacare's taxes would be eliminated in 2017 instead of 2018.
The amendments also addressed Medicaid, which is the country's largest health insurance program and covers about 70 million people, mostly the poor. The changes would allow states to implement work requirements for certain adults, an idea championed by many conservatives, and to decide how they receive federal funds.
Trump, who has not offered Obamacare repeal legislation of his own, did not talk "a whole lot about the healthcare bill except to vote for it," Jones said of the president's trip to Capitol Hill.
The Club for Growth, an influential conservative lobby group, said it would spend at least $500,000 for ads on television and digital platforms urging Congress members to defeat the bill.
The Senate also will vote on the legislation, and more changes could be made. Senate Majority Leader Mitch McConnell said that if the House approved a healthcare bill, he would try to bring it to the Senate floor next week.
(Additional reporting by Jeff Mason, Doina Chiacu, Susan Heavey, Richard Cowan and David Morgan; Writing by Alistair Bell and Amanda Becker; Editing by Frances Kerry and Jonathan Oatis)