Jeff Greenfield: “It is, however, possible to trace the roots of the current Democratic disarray. It comes down to a fundamental misunderstanding of a central political truth, offered by former British Prime Minister Margaret Thatcher. In turning her Conservative Party in a sharp rightward direction, she argued: ‘first you win the argument, then you win the vote.’ “In shaping their sweeping social spending legislation, with a putative price tag of $3.5 trillion, President Joe Biden and the Democratic congressional leaders have argued that this is what the voters chose last November.