"The Sanders voters are very little going over to Trump, but only about between 61 and 68 percent are voting for Clinton right now," he said. "If Sanders' endorsement can bring that up into the 80s, which would be more typical, that would be a big boost for her. Likewise on the Trump side, that 39 percent that would like somebody other than him, they're not voting for Hillary Clinton but they are looking for alternatives. If he can bring them in, that would boost him."