No matter how unfit you might think Donald Trump is for the presidency - no matter how corrupt, reckless, indulgent or disruptive his behaviour seems - nothing restores the sense of his still-better-than-even chance of winning in 2020 like a Democrat TV debate. Americans are overwhelmingly in favour of an alternative to Trump, given consistent polling that shows he suffers a disapproval rating unmatched by any president since World War 2.