Wildly unpopular with much of the American public and blatantly unsuited to the office of the presidency to which both men hope to be reelected, Donald Trump and Joe Biden both seem ripe to be replaced by younger, more competent candidates who evoke less popular revulsion. But while Biden in particular may yet be shuffled aside to make room for somebody else, they currently exist in a state of political symbiosis. Biden and Trump may hate each other, but each owes a strong measure of his political viability to the failings of his opponent. Nobody Likes ThemIn April, AP-NORC polling found “the …