CNN — President Joe Biden is facing more critical moments this week that will test his fraught relationship with his base over Israel’s war in Gaza and potentially widen the partisan split about the Jewish state that has been building for years. Long before the current conflict, polls showed that sympathies among rank-and-file Democrats have been shifting from Israel toward the Palestinians over roughly the past two decades — a period that coincides with almost unbroken right-leaning governments in Israel, mostly led by current Prime Minister Benjamin Netanyahu. Simultaneously, support for Israel over that same long period has markedly increased...