But students, Arab Americans and other Michiganders said in interviews that Mr. Biden’s alliance with Israel’s government was unforgivable and would prevent them from voting for him in November if he did not call for a cease-fire and halt American aid to Israel’s war effort. Perhaps more concerning for the president as he tries to win over skeptical young voters, students with no family connections to the Middle East described their advocacy for the Palestinian cause as part of their social identity.