John McCain has used these weeks of Republican calm to dive into the Democratic lunch pail. This strategy clearly assumes a Barack Obama candidacy. If demographics are destiny -- as the political sages keep telling us -- Democratic demographics may offer some choice cuts to the presumed Republican nominee. By dumb luck, Republicans have chosen their one candidate who projects a moderate image, hasn't alienated Latinos and offers an appealing life story to boot. The core problem for Democrats is that Obama's backers are reliable Democrats, whereas Hillary Clinton's are unreliable Democrats. Less than half of the Clinton voters in...