2) is quite true. Kerry wouldn't have gotten elected if not for the Irish connection. His early opponents portrayed him (quite accurately) as a distant and aloof WASP and only Kerry's Irish name saved him.
1) is much less likely though. How much support has Kerry gotten from the "virulently anti-Israeli Left in America?" Really, how much of a force are they in the Democratic Party? What real evidence do you have? When Wesley Clark and Hillary Clinton "discover" Jewish connections to advance their careers and Democratic candidates routinely pledge themselves to support Israel, how seriously can anyone take that contention?
Some Likud loyalists would claim that anyone who isn't 100% behind Sharon is "anti-Israeli," but given that many Israelis and American Zionists fall into that category themselves, we needn't make that any sort of orthodoxy or paint ourselves into a corner.
I think we are in a transition phase in the US. The radical left is becoming much more anti-Jewish, minute by minute in my observation.
Look at the campuses. Do you think a Likud speaker would be given the same opportunity to speak as a PLP Palestinean propagandist?
The actions of the US in defending itself against terror are now ferociously attacked by the Michael Moore wing of the democrat party, as we speak. How do suppose these same characters feel about Israel defending itself?