This, from recent ADL polling, is pretty interesting: A marked increase in the degree to which Americans approve of pro-Israel lobbying from 1991 to 2007. The percentage of folks who think that pro-Israel lobbies have just the right amount of influence increased from 45% to 55%, while the percentage of folks who think they have too much influence dropped precipitously, from 37% to 16% of the population ("too little" stayed mostly constant, dipping from 9% to 7%).
Matt Yglesias attributes this to the rise of the Christian Zionist movement. Maybe? I'd be interested to see some empirical verification of what accounts for the shift.