it's not so much unity as coalition. it's how adults behave - work together on issues on which you agree, and agree to differ on those you don't. jfk jr has explicitly said that he is free to criticise trump's policies where he disagrees and vice versa. one of the great ironies of us politics is that the democrats could have worked with trump to their advantage - he's a plain vanilla ny democrat and hates the neocons - but instead chose to vilify him.
Catalonia