Alan Dershowitz is a liberal, but more a classical liberal, more in the style of Joe Lieberman. The Democratic Party has long since left him.
Via Townhall:
While Alan Dershowitz is a staunch liberal, he’s threatening to leave the Democratic Party should Rep. Keith Ellison (D-MN) become the next chairman for the national committee. Dershowitz, a renowned attorney and Israel supporter, said he would resign due to Ellison’s positions on the Israeli-Palestinian issue and his association with Louis Farrakhan (via Washington Examiner):
Speaking on Fox Business, Dershowitz said there is a divide in the Democratic Party over Jewish issues, particularly the support of Israel, or lack thereof, offered by the Obama administration.
Dershowitz said Ellison’s past praise of Nation of Islam leader Louis Farrakhan is enough to make him and other Jews leave the party.
“It does, and if they now appoint Keith Ellison, who worked with Farrakhan, to be chairman of the DNC you’re going to see a lot of people leave” Dershowitz said. “I’m going to tell you right here on this show and this is news, if they appoint Keith Ellison to be chairman of the Democratic Party, I will resign my membership to the Democratic Party after 50 years of being a loyal Democrat.”