PHILADELPHIA -- Conservative commentator Rush Limbaugh said Thursday he resigned as an ESPN sports analyst to protect network employees from the uproar over critical comments he made about Philadelphia Eagles quarterback Donovan McNabb.

Limbaugh stepped down from the sports network's "Sunday NFL Countdown" late Wednesday, three days after saying on the show that McNabb was overrated because the media wanted to see a black quarterback succeed.

Democratic presidential candidates and the NAACP had quickly criticized Limbaugh's remark, and Eagles owner Jeffrey Lurie on Thursday accused ESPN of "institutional racism" for hiring Limbaugh in the first place.

At the National Association of Broadcasters' convention in Philadelphia, Limbaugh explained his resignation, saying Thursday: "The great people at ESPN did not want to deal with this kind of reaction. The path of least resistance became for me to resign."

Limbaugh did not directly address media reports that began surfacing Wednesday that the radio talk show host was under investigation in Florida into whether he illegally obtained and abused prescription painkillers.

Talking about his comments about McNabb on ESPN, Limbaugh said Thursday that he had thought about the issue the night before making the comments and wanted to write an essay on it.

"It's something I have believed for quite a while," Limbaugh said. "I don't mean it to hurt anybody. ... It's just an opinion."

Limbaugh has denied that his comments were racially motivated.

"I think what we've had here is a little social concern in the NFL. The media has been very desirous that a black quarterback do well," Limbaugh said on Sunday's show. "There is a little hope invested in McNabb, and he got a lot of credit for the performance of this team that he didn't deserve. The defense carried this team."

McNabb on Wednesday said he didn't mind criticism of his performance but was upset that Limbaugh made his race an issue.

"It's somewhat shocking to hear that on national TV from him," McNabb said. "It's not something that I can sit here and say won't bother me."

Lurie accused ESPN of tarnishing its reputation for the sake of ratings in its decision to hire Limbaugh and its portrayal of NFL players in the fictional series "Playmakers."

"Some of the events of this week are built with institutional racism," Lurie said. "It exists. Let's not hide it. Let's not make us believe the problem is a single person. It's far from that."

A telephone message left with ESPN seeking reaction to Lurie's comment wasn't immediately returned Thursday.

Chris Berman, who anchors the ESPN show, said Wednesday he did not believe Limbaugh's tone or intent was malicious.

"As cut and dry as it seems in print, I didn't think so when it went by my ears," Berman said. "I probably should have looked to soften it."

Limbaugh is the radio host of the politically focused "Rush Limbaugh Show," syndicated in more than 650 markets. He had surgery two years ago to have an electronic device placed in his skull to restore his hearing.

Premiere Radio Networks, which syndicates the politically focused "Rush Limbaugh Show," issued a statement from Limbaugh earlier Thursday saying: "I am unaware of any investigation by any authority involving me. No government representative has contacted me directly or indirectly. If my assistance is required, I will, of course, cooperate fully."

After accepting Limbaugh's resignation on Wednesday, George Bodenheimer, president of ESPN and ABC Sports, said: "We regret the circumstances surrounding this. We believe that he took the appropriate action to resolve this matter expeditiously."

As a half-dozen people protested outside in Philadelphia, Limbaugh told the broadcasters that he was used to scrutiny after 15 years in radio and expects to get attention.

To draw in listeners, "we want controversy," he told the broadcasters meeting. "Nobody tells me what I can and can't say" on the radio, he said.

The New York Daily News, without identifying its source, reported Thursday that Limbaugh was being investigated by the Palm Beach County state attorney's office. The newspaper said it had confirmed the allegations, first reported by the National Enquirer. CNN reported Thursday that sources close to the investigation said Limbaugh had turned up as a buyer of powerful painkillers but that he was not the target of the investigation.

Mike Edmondson, a spokesman for the Palm Beach County state attorney's office, told The Associated Press his office could neither confirm nor deny that an investigation was under way.

The Enquirer had interviewed Wilma Cline, who said she became Limbaugh's drug connection after working as his maid, according to the Daily News. She said Limbaugh had abused OxyContin and other painkillers.

A Miami lawyer for the Clines, Ed Shohat, said Thursday, "The Clines stand by the story." Shohat said neither he nor his clients would comment further.