George Papadopoulos, a former foreign policy adviser to U.S. President Donald Trump's 2016 election campaign, began serving a two-week prison sentence on November 26 after a judge rejected his last-minute bid to remain free.
Papadopoulos was the first campaign aide sentenced in Special Counsel Robert Mueller's investigation into ties between Russia and Trump's campaign. His contacts with Russians and Russian intermediaries during the campaign are believed to have triggered the Russia investigation.
He was sentenced in September after admitting that he lied to the FBI about those contacts.
He had sought a postponement of his prison term until an appeals court ruled in a separate case challenging the constitutionality of Mueller's appointment.
But U.S. District Court Judge Randolph Moss said Papadopoulos waited too long to contest his sentence.
The White House has said Papadopoulos, 31, was a low-level volunteer on the campaign. But he has been a central figure in the Russia investigation.
According to an indictment handed up this summer, Russian intelligence officers had stolen Democratic e-mails that were damaging to Trump opponent Hillary Clinton by April 2016, the same month Papadopoulos was informed by a professor in Malta that Russia had "dirt" on Clinton in the form of "thousands of e-mails."
After an allegedly drunken Papadopoulos related the conversation to an Australian diplomat who passed the information on through intelligence channels, the U.S. Federal Bureau of Investigation (FBI) opened a probe into contacts between the Trump campaign and Russia.
Papadopoulos later used his connections with the Maltese professor, Joseph Mifsud, and other Russian nationals in an attempt to broker a meeting between Trump and Russian President Vladimir Putin.
Papadopoulos repeatedly reported his Russia contacts to the Trump campaign, raising suspicions of collusion at the FBI.