President Trump again brought up the Obama-era uranium deal with the Russians in a tweet Sunday morning, but his claims that the deal reveals collusion between the Clintons and the Kremlin is not supported by evidence.

• What we know: The deal was approved by the Obama administration while Hillary Clinton was Secretary of State. Individuals related to Uranium One and UrAsia — the Canadian companies linked to the deal — donated to the Clinton Foundation.
• What we don't know: Whether Clinton was involved in the decision. There is no evidence that suggests she was, but Congress is looking into it. "Any suggestion that Russian money was directed to influence Clinton's decisions would be explosive. But the fatal flaw in this allegation is Hillary Clinton, by all accounts, did not participate in any discussions regarding the Uranium One sale," the Washington Post reports.

Go deeper: Background on the U.S.-Russia uranium deal