Perhaps most worrisome for the president and his party is that the shift could go beyond Mr. Trump on the ballot this year, and outlast him. Armed with insulated tumblers of wine, the women described how Mr. Trump had turned them off from a Republican Party they once supported, one that they now see as intertwined with the president’s divisive rhetoric.

“I cannot imagine a Republican candidate that I would rally behind,” said Hannah Dasgupta, who is a stay-at-home mother of two school-age children and grew up in a conservative home. “Wow, that’s mind-blowing to think about. That’s a huge departure.”…

Over the past four years, Ms. Dasgupta’s views on abortion have shifted to the left as her opinion of the president has sunk. She has grown tired of explaining his actions — such as his comments in this week’s town hall questioning the effectiveness of mask-wearing — to her young children.

She connects her support of Mr. Biden to her role as a mother, saying that she spends time teaching her children basic skills like sharing and speaking respectfully — traits she believes the president lacks.