"Nearly 20,000 Bay State Democrats have fled the party this Winter, with thousands doing so to join the Republican ranks, according to the state's top elections official." - Matt Stout, Boston Herald, February 29, 2016. Here is the article.
Some speculate what's driving the shift is the Trump phenomenon. He is offering hope, just as Ronald Reagan and FDR (Franklin D. Roosevelt) had. Few can turn that down, not after enduring domestic terrorist attacks and sustained economic uncertainty.
It was Reagan who promised there would be morning in America. The economy turned around. FDR told despairing Americans to try something, anything. They did. And my parents' generation made it through The Great Depression.
Trump may or may not be the guy to make America great again. But many seem willing to give him a chance to at least try to accomplish that.