A conversation among Democrats about whether Barack Obama or Hillary Clinton is better positioned to win the general election can get very slippery very fast. The starting point is fixed: the upcoming race against John McCain. But the polls aren't helpful in showing which candidate has the edge. Hillary Clinton and Barack Obama perform the same, statistically, against John McCain. In the latest Gallup poll, Clinton is running two points ahead of McCain, 47 percent to 45 percent, while Obama is running one point behind, 45 percent to 46 percent. Without clarity in the numbers, the terrain quickly shifts to...