Sanders's ability to draw massive crowds is remarkable. More than 28,000 people deciding to spend a beautiful Sunday in New York City going to a political rally in Brooklyn is amazing. Amazing!
(Sidebar: I looked up some of the crowd sizes that then candidate Obama drew in 2008. Obama had a crowd of 75,000 in Portland, Oregon in March 2008; in October 2008, during the general election, 100,000 people were in St. Louis, Missouri to see him.)
But, but but. Polls in the runup to tomorrow's New York primary suggest that Clinton is likely to not just win but win comfortably.
If Clinton wins on Tuesday, it will be a reminder that crowds are nice but in a state as large as New York they aren't determinative. Remember that Hillary Clinton got more than one million votes to win the New York primary in February 2008; Obama got 750,000 votes to finish second.
If, on the other hand, Sanders wins -- a replay of his come-from-behind victory in the Michigan primary -- people will point to these crowds as the leading edge of that momentum.