The Senate opened debate on a resolution setting in motion the Republican drive to repeal the Democratic-backed 2010 Affordable Care Act, which has helped upwards of 20 million previously uninsured Americans obtain medical insurance.
Obama, who hands over the presidency to Republican Trump on Jan. 20, ventured to Capitol Hill to urge Democratic lawmakers to protect the measure, which is known as Obamacare and is considered his signature domestic policy accomplishment.
Republicans, who will control both chambers of Congress and the White House when Trump takes office, stepped up their rhetorical attack on the law, which they have labeled a government overreach.
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Democrats in turn accused them of trying to rip apart the nation's healthcare system with no firm plan to replace it.
"The Republican plan to cut healthcare wouldn't 'make America great again,'" Senate Democratic Leader Chuck Schumer told reporters, invoking Trump's campaign slogan. "It would make America sick again and lead to chaos instead of affordable care."
Obama "encouraged us to fight," Democratic Representative Elijah Cummings told reporters after the Obama meeting.
Pence, a former member of the U.S. House of Representatives, met Republican lawmakers to plot the path forward on scuttling the law. Afterward, they stepped up their rhetorical attack on Obamacare, with House Speaker Paul Ryan saying the law ruined the American healthcare system.
"The first order of business is to keep our promise to repeal Obamacare and replace it with the kind of healthcare reform that will lower the cost of health insurance without growing the size of government," Pence said at a news conference.
During a news conference, Pence and Ryan offered few details on what a Republican-backed replacement for Obamacare would look like but Ryan said lawmakers will take action that does not "pull the rug out from anybody."
Trump wrote earlier on Twitter that Republicans "must be careful in that the Dems own the failed ObamaCare disaster, with its poor coverage and massive premium increases."
"Don't let the Schumer clowns out of this web," Trump added.
But Schumer said, "They want to repeal it and then try to hang it on us. Not going to happen. It's their responsibility, plain and simple."
'Smooth transition'
The Republicans risk causing chaos in the health insurance market as well as potential political backlash. Pence said repealing it must be done in a way that does not "work a hardship" on the economy or Americans who gained insurance through Obamacare.
Pence said Trump will work in concert with congressional leaders for a "legislative and executive action agenda for an orderly and smooth transition to a market-based healthcare reform system."
Ryan said Republicans have a plan and "plenty of ideas." House Republicans last year offered a proposal that would, among other things, provide refundable tax credits to help people afford their medical insurance premiums.
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White House spokesman Josh Earnest said Republicans must shoulder the blame for the healthcare vacuum that could ensue if they repeal Obamacare without a plan to replace it.
"One of the most articulate Republicans on Capitol Hill is the speaker of the House," Earnest said of Ryan. "And he did a news conference today where he was unable to explain why Republicans have not put forward their replacement plan."
Obamacare helped people obtain insurance by expanding eligibility to the Medicaid healthcare program for the poor and providing government subsidies to help people obtain coverage from private insurers through government-run exchanges.
Trump has vowed to protect some popular parts of Obamacare, such as barring insurance companies from denying coverage to people with pre-existing medical conditions.
But he wants to replace it with a system that is "much better and much less expensive," as he told Reuters on Oct. 25 after premium increases emerged in some healthcare markets.
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The American Medical Association doctors' group urged caution in making changes to Obamacare, which the organization supported.
"In considering opportunities to make coverage more affordable and accessible to all Americans, it is essential that gains in the number of Americans with health insurance coverage be maintained," the AMA said in a letter to congressional leaders.
The AMA said before any action is taken on Obamacare policymakers should lay out for the American people "in reasonable detail what will replace current policies."
"Patients and other stakeholders should be able to clearly compare current policy to new proposals so they can make informed decisions about whether it represents a step forward in the ongoing process of health reform," the group said.
