This is what’s really freaking out Democrats: They know that Brown, after making some real money working for Fox News since his loss to Elizabeth Warren two years ago, wouldn’t even be getting into the race if the political environment weren’t so toxic for Democrats.

Republicans have been white-hot for Brown to get in, and he finally pulled the trigger Friday, establishing an exploratory committee and asserting that “the Obamacare Democrats are on the wrong side” of a big political wave.

G.O.P. leaders think that even if Brown can’t win, he will force Democrats to spend a bunch of money in New Hampshire and curtail what they can spend in other more crucial races like Colorado, Alaska, Montana, Louisiana, Arkansas, North Carolina and Michigan.

Brown jumping in was just one blast of bad news for Democrats. They also lost a special election last Tuesday in Florida by a hair, a defeat David Plouffe called “a screaming siren.” Alex Sink, a promising candidate, sunk after she could not overcome the blast of ads linking her to President Obama and his health care law.