(CNN) President Donald Trump lashed out at Hillary Clinton and the Democratic Party in a tweet Sunday morning, saying the former secretary of state "colluded" with the party in the presidential primary to defeat Sen. Bernie Sanders.
"Is she allowed to so collude?" the President asked. "Unfair to Bernie!"
The tweet is an apparent reference to a cache of nearly 20,000 hacked Democratic National Committee emails released by WikiLeaks nearly one year ago that Sanders' supporters' said bolstered their claims that the party favored Clinton.
The tweet comes as congressional committees and Department of Justice special counsel Robert Mueller continue investigations into Russia's efforts to influence the US election and the Trump campaign's contacts with Russian officials, including allegations of collusion between his campaign and Russia in an effort to defeat Clinton during the presidential campaign. Trump, his campaign and Russian officials have denied any collusion took place between them.
Without mentioning Sanders' name, one of the hacked DNC emails appeared to show a DNC staffer asking others to ask the candidate about his faith, saying it would weaken him in the eyes of Southern voters. Another seemed to depict an attorney for Clinton's campaign advising the committee on how to defend her against an accusation by the Sanders campaign of not living up to a joint fundraising agreement.
The fallout from the release of the emails prompted Sanders and his supporters to call for DNC Chairwoman Debbie Wasserman Schultz of Florida to resign as party chair. Schultz, a Clinton ally, stepped down from that position at the conclusion of the Democratic National Convention.
Clinton spokesman Nick Merrill declined to comment for this story.
Former Clinton campaign manager Robby Mook, a CNN political commentator, said Trump should move on from the election and address concerns over threats to the nation's elections.
"The Washington Post called the Russian intervention in the 2016 election the 'crime of the century,' and much of our campaign and election infrastructure still remains as vulnerable today as it was then," Mook told CNN. "Rather than stoking divisions from the last election, the President should be bringing the country together to defend our country and our democracy."