Over at The New York Times, Nicole Hemmer has a nice piece explaining some of the history of the right's "liberal media bias" charge and how it has left them incapable of seeing anything that happens in the media—even their own media—clearly. It turns out that supporters of Newt Gingrich and Rick Santorum (not to mention Gingrich and Santorum themselves) were shocked to find that their favorite news sources didn't validate everything they believed, including who should win the Republican primary: "this role reversal is the end product of a process that was set in motion by the conservative media. Having spent decades promoting the charge of bias, they have helped strip it of meaning. These days, bias translates roughly to 'reporting something I don't like,' a reflexive defense against stories that cut against conservative interests." Conservatives got so used to seeing bias everywhere that it reached the point where some of them began accusing Fox News of being "liberal" because it wasn't boosting their preferred primary candidate.
That doesn't necessarily mean Fox wasn't biased in Mitt Romney's favor. It well may have been. But conservatives have been so conditioned that not only do they see bias everywhere, as far as they're concerned all bias is, by definition, liberal bias.
But they don't have to worry. Now that the GOP has chosen a nominee, Fox and every other conservative outlet can go back to slamming only Democrats, and there won't be another internecine battle for another four years, or maybe even eight years if Romney wins in November.