If the Democrats choose Joe biden to beat Trump in 2020, they will lose. He has many qualities. He is very experienced, well liked, steady and level headed, already a proven statesman and he understands how the world works. Correction. How the world used to work. That is the problem. It is a bigger problem than his roving hands. Indeed they are a symptom of the problem not the cause. Joe Biden comes from a past with different values, where touchy feely was if not good, not bad either and where power came from the top down, not bottom up. An age of the notion of political class.
Trump is the outsider, chosen because he is not a politician, with no expectation that he should be clean. In fact an acceptance that he would be more effective if he were dirty. So a string of accusing lovers and prostitutes, law suits, investigations, proven lies and U turns make no difference. Indeed to his base it adds to his appeal. If Biden runs against Trump it will be because he is the opposite of all that. He is a pro. Even if he survives the touchy feely stuff, it puts off the women voters. To the young, who are critical to the outcome in 2020, he is a dinosaur from a past from which they believe they have broken free.
The Democrats can win in 2020, but only with a candidate who is all about the future and a product of the bang up to date present. The exception may be Sanders, but my guess is that his values will endure and inspire, but his day, too, has passed.