R if Dems nominate someone who is perceived as an anti-Semite in the same sense Corbyn is (moderately unfairly) smeared as.
The Jewish vote in Britain went Conservative long before Corbyn, he probably merely cemented their hostility to Labour. For example a poll for the Jewish Chronicle conducted before the 2017 election had Labour losing the Jewish vote 77%-13%. But the same poll conducted before the 2015 election (when Labour actually had a Jewish leader) had them down 69%-22%.
Similarly in the US if the nutty far left and their brand of antisemitism ever gain any influence of note in the Democratic Party the same thing will happen with Jewish voters over here. Though the proportion of Muslim voters in the US (undeniably a large source of both Labour votes and antisemitism in the UK) is much smaller and as I understand it Muslims in the US tend to be more progressive than those in Europe anyway so at the moment I doubt the Democratic Party will go the way of UK Labour.
