(Credit: Jim Watson/AFP/Getty Images)

President Obama has many times declared victory for the Affordable Care Act, most recently with the announcement earlier this month that 7 million people have signed up in the law's inaugural year.

Today, with a slight grin, he added a big exclamation point.

Now, 8 million Americans have signed up for health insurance through the exchanges, Obama announced. "This thing is working," he declared.

The White House said 28 percent of sign-ups are between ages of 18 and 34, slightly below insurers expectations but not low enough to break the bank. Millions more signed up for coverage under Medicaid and CHIP. What is still not known is how many people were previously uninsured - and how many have paid for their policies to seal enrollment.

Still, what's clear is that the White House feels enrollment is on the upswing and ready to finally turn the page.

Obama made a full-throated case today for why Democrats should also be confident, embrace health care as an issue and try to turn the tables on Republicans in the fall campaign.

The GOP "is going through, you know, the stages of grief, right? Anger and denial and all that stuff," he said.

"I think what the other side is doing and what the other side is offering would strip away protections from those families and from hundreds of millions of people who already had health insurance before the law passed," Obama said.

"I think that Democrats should forcefully defend and be proud of the fact that millions of people … we're helping because of something we did. I don't think we should apologize for it, and I don't think we should be defensive about it," he said, noting it "is a strong, good, right story to tell."

But Republicans say they are not backing down, vowing to campaign hard on full repeal of the law.

"The White House continues to obscure the full impact of Obamacare," said Brendan Buck, spokesman for House Speaker John Boehner. "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."

For his part, Obama has signaled this week - and said explicitly today - that the White House plans to spend the next few months looking forward and rejuvenating its message on jobs, the economy, and immigration.

"If Republicans want to spend all their time talking about repealing a law that's working, that's their business," Obama said. "I think what Democrats should do is not be defensive, but we need to move on and focus on the things that are really important to the American people right now."