Sanders gambled on Michigan. He traveled all over the state in the days leading up the primary at the expense of campaigning in other places, so his loss there tonight is that much more symbolic. I keep going back to what I heard from Michigan voters over the past few days -- a sense of primary fatigue, alarm over the fighting among the candidates as the contest got heated and a desire to start gearing up for the battle against Trump. Plenty of voters admitted that Biden wasn't their first choice, but they seemed more than happy with him as their candidate. And that, I think, will make it hard for Sanders to keep fighting.