From my checking I found out that the FCC has a "reasonable access" rule, all broadcasters that accept paid advertising must sell at least some time to any qualified candidate.
John Mccain chose the socialist public finance route and is limited to 85 million, Barak H. Obama said first he would also, then changed his mind and took the fund raising route. At last count BHO has raised over 400 million.
My favorite radio station(1360 The Lion out of Johnstown, Colorado) which is very right wing has been running Obama ads, and no Mccain ads.