When Hillary Clinton questioned Gen. David Petraeus last September, she famously said that to believe his description of progress in Iraq required "a willing suspension of disbelief." After the Indiana and North Carolina primaries, the same may now be true about her case for winning the Democratic nomination. It's not that she can't win, but with only 217 delegates up for grabs in the six remaining contests, the scenario for victory has become more fantastical, narrow, and painful.