After a media and political firestorm, Rush Limbaugh issued an apology on Saturday for calling student Sandra Fluke a "slut" on his radio show this week.

Fluke, a law student at Georgetown University who was advocating for health insurance plans to cover the cost of contraception, became the target of a series of attacks by Limbaugh. Besides calling her a "slut," he also called her a "prostitute," said that he wanted her to make sex tapes and post them online, and speculated that she only had a problem paying for contraception because she was having "so much sex."

Limbaugh's comments caused advertisers to flee from his show, and even prompted President Obama to weigh in. The statements also became an issue in the Republican presidential race.

Limbaugh — who has a long history of making incendiary remarks, and is not known to take them back — issued the rare apology on Saturday afternoon, saying he was "sincerely" sorry about his "insulting" characterization of Fluke. But he maintained that the birth control debate was about "personal sexual recreational activities," not any broader health questions, and compared contraception to sneakers.

Even as he walked back his comment, though, there were signs that Limbaugh is not out of the woods yet. Another advertiser, Carbonite, posted a message on Facebooksaying that it was ending its sponsorship of his show.

"No one with daughters the age of Sandra Fluke, and I have two, could possibly abide the insult and abuse heaped upon this courageous and well-intentioned young lady," CEO David Friend wrote. "Mr. Limbaugh, with his highly personal attacks on Miss Fluke, overstepped any reasonable bounds of decency. Even though Mr. Limbaugh has now issued an apology, we have nonetheless decided to withdraw our advertising from his show."

And at least one organization wasn't buying Limbaugh's choice of words.

"Rush's apology wasn't actually an apology," said Shaunna Thomas, a co-founder of UltraViolet, an online advocacy organization that does grassroots work on women's issues. "He did little more than continue to expose himself as the anti-woman and offensive media personality that he is. Our campaign to pressure advertisers to drop their sponsorship of his show will continue next week. No radio show that attacks women should be rewarded with advertising dollars. And more than 84,000 of our members who signed a petition in the last day agree."