The first is that the “enthusiasm gap” matters, and it matters a lot. There is no way that a Democratic candidate for the Senate from Massachusetts, running to fill the seat that the late Ted Kennedy held for decades, should have anything but a cakewalk to victory. It’s true that Martha Coakley ran a mediocre campaign and that Republican Scott Brown ran a very good one, but still, this is Massachusetts we’re talking about. That Obama would have to fly in two days before the vote and stump for Coakley and the Democrats’ filibuster-proof majority was absurd.

But the Brown-Coakley race is just the most stunning manifestation of a phenomenon that we’ve been seeing for at least the past six months. Vocal opponents of the president and the Democratic congressional leadership are eager, motivated and so excited that they can’t wait to grab their “tea party” signs and march around the neighborhood. Vocal supporters of the president are . . . well, at the moment they aren’t even particularly vocal.

There are several reasons for the enthusiasm gap. Some are beyond the president’s control — the decision by Republicans, for example, to take a purely obstructionist stance toward Obama’s domestic initiatives. “No to Washington” is a powerful message at a time when so many Americans are anxious about the future. But the president has ways to counteract such a message, and the fact is that Obama has not given the Democratic Party’s liberal, activist base much to rally around.