The whole point of this thing is not to change the minds of anyone who votes along party lines. It is to pull in the "undecided voters" who MAY normally vote Dim or Rep,but who don't identify with either party and who only pay attention to politics a couple of months every 4 years. Lots of these people never even vote in local or state elections,only Presidential elections.
There are enough of them out there to throw an election either way every 4 years. If the Dims can pull off a political "head shake" and pull in THOSE votes,they can win.
It's the only chance they have,and they know it.
Granted,this Presidential election is pretty unique because there seems to be a LOT of the normal Party Drones that hate Trump so much for "taking it away" from their RINO of choice that they will refuse to vote for him,and some will even vote for the Communist candidate with the D behind it's name. These fools are making it a LOT closer than it should have been,and the more Trump accomplishes the more they hate him. How DARE an outsider like him come in and upset their apple carts!