One of the trickier things to figure out as a political writer is when a scandal, or an impolitic statement, matters. Not matters in a substantive way, but in a political way. The impulse, of course, is to follow each newstory as if its salience in the news cycle corresponded to its actual importance in the campaign. But that's rarely the case. Time passes, comments are forgotten, new gaffes are made, and the election spins on. We've already seen Clinton endure a media feeding frenzy around her position on driver's licenses for immigrants, her remembrances of Tuzla, and her delays in releasing tax returns. We've seen Obama hit by Rezko and Wright. And we've watched McCain mix up al Qaeda members and Iraqi sectarians, pledge himself to 100 years of war, and admit that he doesn't know very much about the economy but was reading Alan Greenspan's memoirs. Any of these could've been a huge deal (and in a couple cases, they were). But what separates them? This is what I've been trying to figure out. In order for a scandal to live on beyond a few news cycles, it needs one of a couple possible qualities. Here's what I've come up with: