Polling is chancy and these days, especially so. 

American Jews are a small group and so polls of them, especially conducted by or on behalf of lefty groups, are stunningly worthless attempts at creating an echo chamber. But the JTA, a lefty propaganda outlet, has really hit the jackpot in pushing a garbage pro-Biden poll.

Another sign in the poll that Trump has alienated Jews is that just 16% of respondents admitted to voting for him in 2016; exit polls at the time showed 24% voting for him. The gap suggests that some respondents might have convinced themselves that they never voted for Trump.

Is that 8% difference a sign that something may be wrong with our poll?

Nah, it must means that 8% hate Trump so much now that they’ve become delusional.

When your explanation for a statistical problem with your poll is that 8% of your respondents are delusional or insane, then you and your poll have big issues.