WASHINGTON (AP) — Looking to undermine rival Joe Biden 20 days before the election, President Donald Trump's campaign has seized on a tabloid story offering bizarre twists to a familiar line of attack: Biden's relationship with Ukraine. But the story in the New York Post raises more questions than answers, including about the authenticity of an email at the center of the story.

The origins of the story also trace back to Trump lawyer Rudy Giuliani, who has repeatedly pushed unfounded claims about Biden and his son, Hunter Biden. Even if the emails in the Post are legitimate, they don't validat...