That’s an astoundingly low number by historical standards. Typical outcomes for American elections have Jews voting 75-83% Democrat.
I think the reasons include the economy, the serious anger at the way Washington has been unable to fix unemployment while saving the banks that caused this mess and, to a lesser extent, a sense that many Dems have turned against Israel.
Having Israel become a partisan issue in DC is a very bad thing. Israel should always remain a bi-partisan issue in the US and those folks who are out there beating this drum should be well aware of the harm they are causing in the long-run.