Speaking in the East Room before a supportive audience Thursday, President Obama said the fact that middle-class Americans were receiving rebates from their insurers was "just an example of the Affordable Care Act doing what it's designed to do: deliver more choices, better benefits, a check on rising costs, and higher quality care."

Obama's remarks came the morning after the House of Representatives took its 38th and 39th votes to repeal or change the health care law, which is shaping up to be a central issue in next year's election. As the Oct. 1 starting date for open enrollment in state and federal health insurance marketplaces approaches, Democrats and Republicans are offering competing data in an effort to sway Americans' attitudes about the landmark bill.

Thursday's speech highlighted a provision in the law requiring insurers to either devote 80 percent of customers' premiums to medical care--rather than administrative costs or executive pay--or provide subscribers with cash rebates. Thirteen million U.S. households received the rebates last year, Obama said, while 8.5 million will be getting them this year, at a rate averaging $100 per family.

Obama was flanked by more than a dozen men and women who had received rebates from insurers including Morgan Theriot, who is self-employed and lives in Silver Spring, Md. Theriot, who was accompanied onstage by her daughter, Grace, and son, Scott, said she welcomed the $267 refund check she received from her insurance company last summer. "The Affordable Care Act is working for people like me," she said, noting that she had gotten "used to seeing my premiums going up and up, without knowing why."

The president noted that other Americans had benefited as well, such as Chicago resident Dan Hart, who was onstage and last summer "got a check in the mail for $136. And Dan is a father of two, and as any parent will tell you, those kids, they suck up a lot of money."

Republicans said these rebates would do little to cushion the financial blow for those who will face rising premiums, as projected by the Congressional Budget Office.

“In other words, if you’re a family in Covington facing a $2,100 premium increase under Obamacare, then, really, what would you rather have: a check for $100 or so, or a way to avoid the $2,100 premium increase in the first place?" asked Senate Minority Leader Mitch McConnell (R-Ky.) in a floor speech Thursday. "I think the answer’s obvious. And I think most Kentuckians would agree that this is just another sad attempt by the administration to spin them into wanting a law they don’t.

Administration officials say that the initial estimates CBO prepared when the law was passed are no longer accurate. The Department of Health and Human Services issued a new analysis Thursday of projected 2014 premium rates in 11 states suggesting that the rates for plans covering 70 percent of subscribers' health care costs will be on average 18 percent lower than CBO originally predicted.

Obama, for his part, made it clear in his speech he will try to counter the GOP offensive against one of his first-term's signature accomplishments.

"Now, I recognize that there are still a lot of folks -- in this town, at least -- who are rooting for this law to fail. Some of them seem to think this law is about me.  It's not. I already have really good health care," he said, prompting laughter from the audience. "Affordable health care is not some privilege just for the few. It’s a basic right that everybody should be able to enjoy."