Adam Schiff has said that there is an abundance of evidence that points to collusion between the Trump campaign and Russia.

The top Democrat on the House Intelligence Committee, Adam Schiff, said on Wednesday that there is a copious amount of evidence pointing to collusion between the Trump campaign and Russia, notes USA Today. "There is certainly an abundance of non-public information that we've gathered in the investigation," he told reporters gathered at an event hosted by the Christian Science Monitor in Washington, D.C. "And I think some of that non-public evidence is evidence on the issue of collusion and some...on the issue of obstruction." 
"There is already, in my view, ample evidence in the public domain on the issue of collusion if you're willing to see it," Schiff also noted. He did state that while he thinks there is sufficient proof, "All of this is evidence of collusion. Now, I've never said that there was proof beyond a reasonable doubt. That's for Bob Mueller to decide. But to say there's no evidence of collusion, you'd have to ignore all this."  Among those who have repeatedly denied that evidence of collusion exists is President Trump.  He has often generously peppered statements with the words "no collusion" and called the investigation into the matter a "witch hunt." 
"The single greatest Witch Hunt in American history continues," Trump tweeted on January 10. "There was no collusion, everybody including the Dems knows there was no collusion, & yet on and on it goes. Russia & the world is laughing at the stupidity they are witnessing."