Since I've already written about the underappreciated upside of Sarah Palin's nomination, I now offer the contrary view of why the relatively minor problems that have surfaced in the last few days seem to have unusual traction.
Reporters have information about candidates that they want to share but feel constrained not to. The constraint may come from ethical concerns, from editors, or from peer pressure, and it may be controversial: if you read any left-leaning citizen journalism, for example, you probably know that John McCain has said appalling things to his wife in front of reporters, but mainstream journalists have shown no inclination to recall that fact in the context of McCain's policy positions that relate to women's rights and issues. Many Republicans feel that Barack Obama has similarly been let off the hook for statements he and his proxies have made.
Now may observers are noting that the press seems unusually tenacious in examining Sarah Palin. I've seen some potential explanations and can imagine others, from sexism to religious bias to media resentment.
I suspect something a little different: my guess is that reporters have been struggling for a while with how to convey the fact that John McCain has been screwing up major points of foreign policy, making impetuous decisions, and generally exhibiting a lack of managerial control. This information dribbles out here and there, but no story has brought it all together in the way that the Palin appointment has.
On the heels of a Democratic Convention that, among other things, displayed the Obama team's formidable managerial and logistical skills, the Palin appointment highlighted McCain's impulsive hotheadedness in a way that had nothing directly to do with foreign policy. Suddenly, reporters who felt they could not ethically say, for instance, that McCain's reaction to the Georgian crisis was ludicrously belligerent and ill-considered, could say instead that it seems awfully strange to choose a Vice President at the very last minute with very little information in hand.
Hence the McCain campaign's furious efforts to defend the vetting process--a process that, after the announcement of the result, seems much less important than McCain's alarmingly shaky grasp of the geography and ideologies of the Middle East. Everybody involved understands that the argument over the vetting process is the publicly acceptable proxy for the argument over McCain's stability.
I could be wrong about this case, but I am more confident in the general assertion that many times the press seems hung up on a relatively minor political story, we are seeing journalists attempt to convey something they've been uncomfortable about keeping quiet.