WASHINGTON (AP) — The bombshell revelations that President Donald Trump paid just $750 in federal income taxes the year he ran for office and paid no income taxes at all in many others threaten to undercut a pillar of his appeal among blue-collar voters and provide a new opening for his Democratic rival, Joe Biden, on the eve of the first presidential debate.

Trump has worked for decades to build an image of himself as a hugely successful businessman — even choosing "mogul" as his Secret Service code name. But The New York Times on Sunday revealed that he paid just $750 in federal income taxes...