The Federal Bureau of Prisons on Monday said Papadopoulos arrived at a minimum-security prison in Wisconsin.
A federal judge threw out Papadopoulos' last-ditch effort to delay his sentence on Sunday after lawyers for the special counsel's office argued that through his tweets, he "made a variety of public statements that appear to be inconsistent with his stated acceptance of responsibility at sentencing."
Papadopoulos went further on Monday, saying that he's "never met a single Russian official" in his life.
While the entrapment angle remains unproven, Mifsud's own lawyer recently admitted that the professor has worked closely with western intelligence in the past and is currently on orders to lay low until after special counsel Robert Mueller is done with his investigation.
Mifsud allegedly told Papadopoulos that the Russians have dirt on Hillary Clinton in the form of emails. Papadopoulos allegedly bragged to an Australian official about that, who later tipped off the FBI, sparking what is now called the "Mueller probe."
The Australian official, Alexander Downer, and Mifsud, both have connections to former British intelligence operatives and the Clinton Foundation. Mifsud, for his part, claims that it is the only foundation that he is a member of, while Downer has helped secure funding from the Australian government for its initiatives.