Whoa – from Rasmussen:

In the end, Brown pulled off the upset in large part because he won unaffiliated voters by a 73% to 25% margin. The senator-elect also picked up 23% of the vote from Democrats. [Our polling shows that 53% of voters in Massachusetts are Democrats, 21% Republican and 26% not affiliated with either party.]
Coakley also barely carried a usually reliable Democratic constituency. Union workers went for her by just six points, 52% to 46%.

Again, the independents won it, just as they did in New Jersey and in Virginia.

The trending showing the number of self-identifying Democrats is decreasing:

In December, the number of Americans identifying themselves as Democrats fell to the lowest level recorded in more than seven years of monthly tracking by Rasmussen Reports.

Currently, 35.5% of American adults view themselves as Democrats. That’s down from 36.0 a month ago and from 37.8% in October.

Related:

Conservatives Maintain Edge as Top Ideological Group

Conservatives Finish 2009 as No. 1 Ideological Group