MADISON, Wis. -- Clear Channel Radio officials said that high school and college sports are a better fit for listeners in Madison than progressive talk radio.

For some, those might be fighting words in a city where "Impeach Bush" signs are common.

Clear Channel is replacing Air America Radio at "The Mic," 92.1 FM, with Fox Sports Radio.

The plan has caused a backlash with some advertisers threatening a boycott. More than 5,000 people have signed a petition and a rally is planned on Tuesday night to get Clear Channel to reconsider.

Jeff Tyler, the company's market manager in Madison, said that too many advertisers stayed away from the station because of opposition to the 2-year-old format. It mixes nationally known liberal talkers such as Al Franken with local hosts who discussed everything from city politics to animal rights.

Tyler said that the station is making money but has consistently ranked dead last out of 14 Madison stations that report earnings.