CLEVELAND – It started out civilly enough, with President Donald Trump striding deliberately to his lectern, and Democrat Joe Biden nodding to his opponent and offering a “How you doing, man?”But within 15 minutes, the debate had devolved into a series of endless interruptions, with Biden, seemingly unable to complete a sentence, finally blurting out, “Will you shut up, man?”It was a chaotic and unusually bitter first presidential debate of the 2020 general election, made all the more unusual by the the ongoing coronavirus pandemic.