In a long-term effort aimed at weakening his influence, Rush Limbaugh's opponents are starting a radio campaign against him Thursday, seizing upon an unnecessarily crude comment the radio talk show host recently made about a Georgetown law student.

Media Matters for America is using a past campaign it used against Glenn Beck as a template. But with Limbaugh they're going after bigger game. He's already fighting back and the liberal media watchdog group's stance has provoked concerns that an effort to silence someone for objectionable talk is in itself objectionable.

Media Matters is spending at least $100,000 for two advertisements that will run in eight cities.

The ads use Limbaugh's own words about student Sandra Fluke, who told congressional Democrats that contraception should be paid for in health plans. Limbaugh, on his radio programs, suggested Fluke wanted to be paid to have sex, which made her a "slut" and a "prostitute." In return for the money, he said Fluke should post videos of herself having sex. Limbaugh later apologized.

In one of the anti-Limbaugh ads, listeners are urged to call the local station that carries Limbaugh's program to say "We don't talk to women like that" in our city.

Ad time was purchased in Boston; Chicago; Detroit; Seattle; Milwaukee; St. Louis; Macon, Ga.; and Cedar Rapids, Iowa. The cities were selected to support active local campaigns against Limbaugh or because of perceptions Limbaugh may be vulnerable in that market, said Angelo Carusone of Media Matters.

A spokeswoman for Premiere Radio Networks, which syndicates Limbaugh's show to nearly 600 radio stations nationally, said Media Matters has gone beyond criticism of Limbaugh's words to an attempt to silence him and intimidate advertisers.

"This is not about women," said Rachel Nelson, Premiere spokeswoman. "It's not about ethics and it's not about the nature of our public discourse. It's a direct attack on America's guaranteed First Amendment right to free speech. It's essentially a call for censorship masquerading as high-minded indignation."

Limbaugh, on his radio show Wednesday, said he's being targeted in an attack that was long-planned.

"They're not even really offended by what happened," he said. "This is just an opportunity to execute a plan they've had in their drawer since 2009."

Determining how much of a financial impact the Fluke comments have already had on Limbaugh is murky business.

Radio stations in Hawaii and Massachusetts have dropped his show. Media Matters claims that 58 companies have specifically asked that their ads be excluded from Limbaugh's program. Radio-Info.com's TRI Newsletter said Premiere has circulated a list of 98 advertisers who want to avoid "environments likely to stir negative sentiments," essentially all politically pointed talk shows.

The University of North Carolina is one organization wanting to sever any Limbaugh connection.

UNC Chancellor Holden Thorp told Carolina Connection reporter Michael Tomsic that because of Limbaugh's "offensive and inappropriate" comments, the school is asking 106.1 WRDU-FM in Raleigh not to promote Rush Limbaugh's radio show during Tar Heel sports broadcasts, and vice versa. The school's men's basketball team is among this year's NCAA basketball tournament Sweet Sixteen.

Whether the advertisers return to Limbaugh's program is another question. Limbaugh has a daily audience estimated at between 2 million and 3 million people, according to Talkers magazine.

"I suspect some people will permanently stay away," said Tom Taylor, executive editor at Radio-Info.com. "I suspect some people will drift back to Rush. What you won't see is a press release of someone saying, 'Hey, we're back with Rush!'"

While a law student, Carusone was active in a campaign to reach Beck's advertisers that began after the commentator said in July 2009 that President Barack Obama had "a deep-seated hatred for white people." Eventually, more than 400 advertisers said they didn't want to be part of Beck's show and, for the Fox News Channel, the ad revenue was nowhere near what would be expected for a TV show as popular as Beck's. When Beck left Fox in June 2011 to take his show to the internet, the parting was mutual.

The idea with Limbaugh is similar: Take advertisers away so rates go down, Carusone said. Couple that with the need to keep track of ever-changing lists of who will advertise with Limbaugh and who won't, and Media Matters hopes that station managers, market by market, may someday conclude that it's just not worth the trouble.

Conveniently, many stations will soon have a choice. Former GOP presidential candidate Mike Huckabee is launching his own syndicated radio show in April that will air at the same time as Limbaugh's, and Huckabee's backers are touting the show as a more civilized alternative.