Presumptive Democratic presidential nominee Joe Biden, pictured on Wednesday, has raised questions about whether a senator leading an investigation into him is at the receiving end of a foreign influence operation.

NEW CASTLE, DE – JULY 21: Democratic presidential candidate former Vice President Joe Biden speaks about economic recovery during a campaign event at Colonial Early Education Program at the Colwyck Center on July 21, 2020 in New Castle, Delaware. Biden took no questions from the press at the conclusion of the event. (Photo by Drew Angerer/Getty Images)