Does Obama need Fox?

Following Fox News Channel's airing of the report (originally in Insight Magazine, whatever that is) that Obama attended a madrassah, the Obama campaign apparently froze out Fox of access for a while. The quesiton is, could they just freeze out Fox all the way? Doesn't Fox just get some of their legitimacy because people feel they have to go on to get their message out, and then, the next candidate has to go on too because the first one did? What if all the major Democratic candidates made a pact not to give them access?