That depends on what topics he campaigns on. If he hits the correct Republican notes, he can siphon votes. That’s just what Perot did- a careful triangulation of several hot buttons for Republicans and poison pills for Democrats, and Billy Jeff won with 48% (or something) of the vote.
It requires MSM complicity, but that should be no problem.
He won’t hit the correct Republican notes. He’s at least as liberal as Her Heinous, and not shy about it. Pop some popcorn and enjoy. The Dems chances in ‘08 just got a lot worse.
But look at the hot buttons he's actually hitting: gun control, same-sex marriage, and abortion -- for all of them, he takes the Democrat line.
Moreover, Bloomberg is actually from New York; he's an ACTUAL northeasterner -- as such, he could well tie up a lot of the Eastern Seaboard's Democrat votes.
And we cannot forget the most important of all: he is not Hillary Clinton.
At the same time, Bloomberg is not much of a threat to take Republican votes -- each of those same hot-button issues turns off large groups of R voters.