Americans for Prosperity is intensifying the pressure on congressional Democrats by launching yet another round of TV commercials in Florida Thursday, expanding its anti-Obamacare campaign into a new House district.

The conservative advocacy group plans to announce that it will spend nearly $400,000 running ads hitting Reps. Alan Grayson and Joe Garcia for backing President Obama’s health-care law. AFP had already spent about $140,000 on ads against Garcia in November, but the buy against Grayson – for now, just online – is the group’s first swipe at the outspoken Democrat this cycle.

“President Obama told the lie of the year,” says a female narrator in the Grayson ad, referring to the president’s pledge that people would be able to keep their health insurance plans if they liked them. “And Congressman Grayson backed him up.”

The spot includes a clip of Grayson saying, “Everyone will love this bill.”

The narrator concludes, “Tell him his vote for Obamacare is hurting Florida families.”

AFP, the main political arm of a donor network backed by the billionaire industrialists Charles and David Koch, has spent more than $27 million since August on spots that challenge vulnerable Senate and House Democrats for their support of Obama’s controversial health-care legislation. In doing so, it has cemented its role as the dominant player in the 2014 midterms, and the GOP’s most valuable ally. As a tax-exempt "social welfare" group, AFP is not required to disclose its financial backers, as political committees must.

“These ads are really part of a wall-to-wall effort that Americans for Prosperity has led for five years in opposition to Obamacare,” Slade O'Brien, AFP’s Florida state director, said in a statement. “From writing Congress, to grassroots rallies and educational events, to radio and television campaigns, our members have stood in opposition to this law from every angle. Reps. Garcia and Grayson both know the President told the 'Lie of the Year,' but they're still supporting the Obamacare mess and all the attendant pain it inflicts on patients.”