From your article...
Nearly 20,000 Bay State Democrats, or 1.3 percent of the party's Masachussetts population, left to vote in the Republican primary Tuesday. More than 16,300 of that group have "unenrolled" or become Independent voters, while 3,500 have joined the GOP.
So ... %17 of 1.3% of the registered democrats switched from democrat to republican...
That is 'a lot'?
Although Donald Trump has convinced some Democrats to switch parties, his candidacy has also had the opposite effect on some Republicans. A net 5,911 GOP voters have denounced their Republican roots.
(5911 is also about 1.3% of the registered republicans in MA)
Is that also 'a lot'?
Reading is fundamental, Steve- look into it....
There are, as of last month, 1.49 million registered democrats in MA, and 0.468 million republicans...
http://www.sec.state.ma.us/ele/eleenr/enridx.htm