Nor should it be, according to Jonathan Bernstein:

[T]here is no actual good reason for either parties or the press to be fair to candidates. They should be fair to voters, either individually or as they exist in organized groups and constituencies. But candidates? Nope. There is simply no reason for the press to automatically believe that vanity candidates Newt Gingrich and Herman Cain are entitled to the same level of coverage as plausible nominees Rick Perry and Mitt Romney.

Steinglass echoes.