Ever eager to provoke, Rush Limbaugh has now succeeded into drawing the White House into a skirmish. The spark: Limbaugh telling his talk show fans that a law student was a "slut" for her testimony to Congress about the need for birth control coverage.

On Friday, two days after Limbaugh's tirade, President Barack Obama called student Sandra Fluke to commend her willingness to speak out and share her dismay over the slur.

The White House termed Limbaugh's remarks "reprehensible," and the criticism was echoed by Democratic members of Congress, women's groups, and the administration and faculty at Georgetown University, the Roman Catholic school in Washington that Fluke attends.

Calls for Limbaugh's sponsors to pull their ads from his show rocketed through cyberspace, and several companies, including Quicken Loans, LegalZoom online legal document service, and bedding retailers Sleep Train and Sleep Number, bowed to the pressure.

For Obama, it was an emphatic plunge into the latest flare-up on social issues. Democratic officeholders and liberal advocacy have accused Republicans of waging a "war on women" because of GOP stances on contraception and abortion rights, and Limbaugh's disparaging remarks were seen as an escalation. READ MORE