The controversy that swirled around Congress this week after Rep. Ilhan Omar insinuated that politicians only support Israel because of donations from wealthy Jews died down as quickly as it began. Publicly rebuked by leaders of her own party for using “anti-Semitic tropes,” the freshman Democrat issued an apology. But while this episode was short, the already tricky politics of Israel are likely to keep coming up — and keep getting trickier for Democrats. As the Democratic Party gears up for a contentious 2020 primary, many observers are warning that the grassroots of the party may not be in sync with the traditionally strong support of Israel among lawmakers of both parties.