The conventional wisdom is that Massachusetts is the most Democratic of states, home to the Kennedys and Elizabeth Warren. So Donald Trump holds a rally at a Massachusetts arena which holds 8000 and fills it SRO. See the Washington Post story and photo of the crowd.
People stood in line for hours in sub-freezing cold to get in. Sure, he's a celebrity and people just want to see him - but lining up in the cold?
The pundit class continues to underrate Trump's chances, he's made them look silly so far. If somebody asks you to bet against Trump, make 'em give you very good odds.