MEDIA, Pa. — There is potential good news for Hillary Clinton in the politically crucial Philadelphia suburbs: A parade of Republicans said in interviews this week they could not vote for Donald J. Trump.

But there was also bad news: If Mrs. Clinton ever had a chance to win these disaffected Republicans, she has come close to forfeiting the opportunity after the F.B.I.’s rebuke of her handling of classified government emails.

Nearly two dozen Republican professional men and women disavowed Mr. Trump in interviews on the pedestrian-friendly downtown streets of these middle-class towns, whose educated voters are even more crucial to winning Pennsylvania than blue-collar workers in the Rust Belt, who receive more attention politically. In yoga studios, taco bars and coffee shops, Republican after Republican called Mr. Trump ineligible for their vote.

“I read an article that global terror threats would increase if Donald Trump becomes president, and that’s scary,” said Jessica Devers, 25, a paralegal from Wallingford, who voted for Mr. Trump in the Pennsylvania primary but does not plan to in the fall.