Bernie Sanders:

It is beyond comprehension, the degree to which the Democratic party nationally has essentially abdicated half of the states in this country to rightwing Republicans, including some of the poorest states in America, those in the south,” Sanders said. “The reason I go to Kansas and many so-called red states is that I will do everything that I can to bring new people into the political process in states which are today conservative. I do not know how you turn those states around unless you go there and get people excited

You also can’t assume you have a state won. I believe the 2016 Presidential election would have a different outcome had Hilary actively campaigned in Michigan and Wisconsin.