It just so happens that there are more Democrats (not many mind you) in Congress than Republicans that support a 2 state solution for the Israelis and the Palestinians. It appears therefore, that J Street supports the Democratic Party more than the Republican Party. In fact J Street will support anyone no matter what his/her political affiliation who wants the U.S. to work towards a political solution to the Palestinian, Israeli conflict.
Israeli forces shoot, lightly wound Palestinian they say was fleeing security check (Haaretz)
from the article: What's wrong with J Street?