Mr. Biden’s announcement that he had paused a shipment of 3,500 bombs to Israel and would not help with a ground invasion of Rafah was a sea change in U.S. policy that Arab American and Muslim leaders have demanded for months. But those who desired it the most have long ago written off the administration as complicit in a war that Gaza officials say has killed more than 34,000 people, arguing it was, essentially, too little, too late.

“The president’s announcement is extremely overdue and horribly insufficient,” said Abbas Alawieh, one of the leaders of a protest-vote movement against Mr. Biden that began in Michigan this year. “He needs to come out against this war. Period. That would be significant.”

Mr. Biden’s White House aides engaged in considerable outreach at the outset of the Democratic primary season, when the movement to cast protest votes in early states emerged as a surprising political headache. A cadre of high-level aides traveled to Dearborn, Mich., and Chicago to demonstrate their interest in listening, but Arab American leaders told them that without a momentous shift in U.S. policy — such as support for a permanent cease-fire — there was no need to keep talking.