President Barack Obama announced Thursday that over 8 million Americans have signed up for health insurance through the Affordable Care Act.

Obama trumpeted the figure, which exceeded projections, during an unannounced visit to the White House briefing room, saying that more than 1 in 4 (28%) who signed up for coverage on federally controlled marketplaces are between 18 and 34 years old. The first enrollment period concluded at the end of March, but those who began applications for coverage before that date had until this week to complete them.

The 28% figure is below Administration targets for young and healthy individuals, but the White House has said it is confident the exchanges will still function at that rate, noting that the figure is almost identical to that in Massachusetts when the state instituted its exchange in 2006–07.

As the midterm elections approach, Obama encouraged members of his party to hold their ground on the law, even as some vulnerable Democrats seek to hide from it. “I think that Democrats should forcefully defend and be proud [of the law],” Obama said. “I don’t think we should apologize for it, I don’t think we should be defensive about it.”

Obama criticized states that have rejected federal funds to expand Medicaid, saying the decision by Republican governors and legislatures “frustrates” him. “You got 5 million people who could be having health insurance right now at no cost to these states — zero cost to these states — other than ideological reasons they have chosen not to provide health insurance for their citizens.”

“This thing is working,” Obama said, highlighting the rise in the number of insured Americans and a slowing in health care cost increases, before attacking congressional Republicans who are focused on repealing the law. “I think we can all agree that it’s well past time to move on,” he said.

“The point is the repeal debate is, and should be, over,” he added.

Congressional Republicans rejected Obama’s call within minutes of the announcement:

Brendan Buck, a spokesperson for House Speaker John Boehner, said the White House was hiding the true, negative impact of the law. “Beyond refusing to disclose the number of people who’ve actually enrolled by paying premiums, the President ignores the havoc that this law has wreaked on private plans that people already had and liked,” he said. “Surveys have consistently shown that the overwhelming majority of those who signed up already had insurance. Had this law not led to millions of Americans receiving cancelation notices, many would not have had to sign up for this government-run program. What America really needs is a health care system that is more affordable, more accessible and of the highest quality, and that’s what House Republicans are working toward.”

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