CHARLESTON, South Carolina – Bernie Sanders and Hillary Clinton clashed on health care at the NBC News/YouTube debate here Sunday night, hours after Sanders rolled out the long-awaited details of his single-payer health care plan.

The exchange encapsulated the philosophical and strategic divide between the candidates, with Sanders urging voters to “think big” and Clinton reminding the audience of the challenge in changing the health care system.

Clinton advocated for incremental evolution over revolution, saying “details matter” and arguing that the Affordable Care Act, which she called one of the biggest accomplishments in the history of the Democratic Party, should not be jeopardized. “I don’t want to see us start over again with a contentious debate on health care,” she said.

Clinton noted that even when President Obama had large majorities in the House and Senate to work with during his first term, he was still unable to get a public option added to the Affordable Care Act – let alone single payer.

Sanders meanwhile, focused on the people who are still not insured or are underinsured under Obamacare. “The vision of Franklin Roosevelt and Harry Truman was health care for everyone,” he said, stressing the last word.

And he defended himself from accusations lodged by Clinton that he wanted to dismantle Obamacare. We’re not going to tear up the ACA, I helped write it,” he said. Responding to the failure of Vermont to enact single payer, Sanders seemed to blame the state’s governor. “You might want to ask the governor about that. I am not the governor,” he said.

“Yes, some middle class families would be paying slightly more in taxes,” Sanders said, but he added that families would save much more in reduced premiums and health care costs.

view photo essay Democrats face off in NBC News-YouTube debate The 2016 Democratic presidential candidates gathered for their first debate of 2016 Sunday night – and there were fireworks.

Just two hours before the start of the debate, Sanders released the broad details of a single payer health care plan that would cover Americans from birth through end of life and would decouple health coverage from employment. The plan, which the campaign said would build on the 50-year Medicare program, would cost an estimated $13.8 trillion over 10 years and would be financed by a 2.2 percent premium imposed on all households and a series of hikes on the richest Americans.

The plan would effectively eliminate the private health insurance industry, with the federal plan replacing current coverage mechanisms.

The long-awaited release of Sanders’ health care proposal came just two hours before he was set to meet rival Hillary Rodham Clinton in a nationally televised debate on NBC, and after days of intensifying combat between the Clinton and Sanders camps over which candidate is offering the most comprehensive and cost-effective health care plan.

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Clinton, who has vowed to embrace and improve upon the Affordable Care Act if elected president, has criticized Sanders for withholding key details of his single payer proposal until now and – more importantly – how he would finance it. Her campaign has also asserted that Sanders’ efforts would weaken the ACA, better known as Obamacare – the President Obama’s signature domestic policy achievement.

The plan, as outlined by Sanders’ campaign, would eliminate private insurance but allow people to see the provider of their choice with nothing more than a federally administered insurance card granting them access to care. It promises to provide Americans with the full spectrum of health care, from inpatient emergency care to vision correction to mental health, along with prescription drugs and devices. And it promises to provide all of that with no copays or deductibles. “As a patient, all you need to do is go to the doctor and show your insurance card,” the plan reads.

Sanders’ campaign claims his plan will cost about $14 trillion over 10 years, but cost $6 trillion less than the current healthcare system over the decade. They say it will save average families over $5,800 per year in premiums and deductibles, and save businesses an average of $9,400 a year in health care costs they pay per employee.

The plan is financed mainly by higher taxes on the wealthy, but would include costs on the middle class. It would charge everyone 2.2% of their taxable income as a health care premium. And it would charge employers 6.2% of the wages they pay based on the existing payroll tax system.

The Sanders campaign claims these are not taxes but premiums, and would replace the premiums families and employers are already paying to private health insurance companies. Clinton is sure to disagree with that characterization.

Meanwhile, the the plan would raise another $110 billion from an income tax hike on those making more than $250,000 a year, with top marginal tax rates moving to 52% for income over $10 million a year.

Sanders would also tax capital gains and dividends, which are currently charged a lower rate, the same as wages. While that would primarily impact the wealthy, it would also hit anyone who holds stocks and bonds. And the plan would eliminate another $310 billion per year in so-called tax expenditures related to health care, especially the exemption on taxes for health benefits.

The financing mechanism seems to contradict a claim Sanders made last month, when he said on NBC’s “Meet the Press” that he would raise taxes on the middle class only to pay for a paid family leave plan, which is financed by a small increase on payroll taxes.

To back up the numbers, the Sanders campaign provided an analysis from University of Massachusetts professor Gerald Friedman, who has designed and analyzed several single payer plans.

The math could not be immediately verified, but the plan is sure to be scrutinized in coming days by critics, fans, and independent analysts.

In response to the plan, Clinton campaign spokesperson Brian Fallon accused Sanders of making up his plan as he goes along. “Senator Sanders has been changing a lot of positions in the last 24 hours because when his plans and record come under scrutiny, their very real flaws get exposed,” Fallon said in a statement. “Details matter—and Senator Sanders is making them up as he goes along.”