WASHINGTON - The Senate's top Democrat is calling on congressional Republicans to stand behind special counsel Robert Mueller's investigation into ties between Russia and Donald Trump's 2016 presidential campaign.

  

In a statement Sunday, Sen. Chuck Schumer of New York condemned Trump's suggestion that Mueller's investigation be shut down.

  

Schumer says "Republican colleagues, particularly the leadership" need to make it clear that "firing Mueller is a red line for our democracy that cannot be crossed."

  

Trump complained anew in a tweet late Saturday that the Mueller probe was a "witch hunt" and "should never have been started in that there was no collusion."