The decades-long allegiance of Jewish voters to the Democratic Party is under unprecedented stress, threatened by a combination of changing demographics and the concerted Republican effort to depict President Barack Obama as unfriendly to Israel.

Nowhere are the stakes higher than South Florida, home to 490,000 Jews who make up a voting bloc powerful enough to influence national elections. Though a small percentage of the overall population, Jews vote at a higher rate than virtually every other slice of the electorate.

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