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Four sponsors have severed ties with Rush Limbaugh's radio show after the outspoken host called law student Sandra Fluke a "slut" and a "prostitute."

National advertisers LegalZoom, Quicken Loans and Sleep Number along with West Coast ad buyer The Sleep Train announced this week they were pulling all advertisements.

"We don't condone negative comments directed toward any group. In response, we are currently pulling our ads from Rush with Rush Limbaugh," Sleep Train wrote on Twitter.

Sandra Fluke, a Georgetown Law Student, was thrust into the spotlight this week after Limbaugh called her a "slut" for her stance on a new insurance mandate that requires employers to cover the cost of contraception.

"What does it say about the college co-ed Sandra Fluke, who goes before a congressional committee and essentially says that she must be paid to have sex, what does that make her? It makes her a slut, right? It makes her a prostitute," Limbaugh said Wednesday.

The radio host's comments caused customers to lobby advertisers to pull their money from the show or risk losing business.

The California-based Sleep Train has enjoyed a relationship with Limbaugh since it opened its first store in 1985.

Founder Dale Carlsen told the Sacramento Bee in 2006 that Limbaugh was introduced to him through an ad sales representative.

"The ad guy said, 'Now he's a little bit controversial, but he needs a bed, would you take care of him?' " Carlsen said. "I needed every sale that I could get at that time, so I said, 'Yeah, bring him in and I'll take care of him.' "

Not only did advertisers feel the heat, bit Limbaugh's shot at Fluke has been drawn into presidential politics. President Obama called Fluke Friday to make sure she was okay, Fluke said.

The three Republican candidates have been less eager to discuss Limbaugh, a favorite of conservatives.

When asked about Limbaugh today, Newt Gingrich criticized Obama's phone call to Fluke.

"I think the president will opportunistically do anything he can," Gingrich said after a rally at the Back Porch Saloon. "I think the most important use of language in the last week has been the president's apology to religious fanatics, and I want to stay focused on what the president has said, and I think what he said was inexcusable and is exactly the wrong policy at a time of life and death, and playing political games is irrelevant as far as I'm concerned."

Mitt Romney was more measured in his response.

"I'll just say this, which is, it's not the language I would have used," Romney told an Ohio crowd.

Rick Santorum called Limbaugh's comments "absurd," but said Limbaugh was just being an entertainer.