I find this subject fascinating, because I'm part of a group which (up until just recently) was also a "given" constituency for the Dems: American Jews.
For a long, long time now, I've been virtually the only conservative in any gathering of Jews in which i found myself... but (and this is the good news, I think) I find that changing more and more, ever since 9/11, and GWB's principled defense of Israel. I don't think it's in any way impossible -- all things being equal; and barring any sudden surprises, between now and 11/04 -- for our party, at long last, to score as much as 40% (or more) of the Jewish vote, next time out.
(That may not seem like much, I know... but: considering how monlithic the Jewish vote has always been for the Dems in the past...)
Suddenly: states such as New York, and Illinois -- areas usually all but conceded to the Dems, electorally -- are "in play" again, if that happens. :)