A few of us oldsters recall a time when the party out of power assumed the mantle of "The Loyal Opposition".
By and large, Republican types at the national level have still acted in this manner, muting their opposition to a new Administration, respecting what used to be described, somewhat quaintly at this remove as a "honeymoon period".
But for Democrats, not only did the "honeymoon" never begin, it's never going to happen. Today's Progressives believe that they and only they have a legitimate claim to running the government, and that when Republicans win, it must be a result of dishonesty, deceit or more simply, the stupidity of American voters.
Democrats are still the party of Government. Outside of Congress and, soon the Presidency, they control its institutions and its bureaucracies and they will be damned if they let go without a fight. Even more importantly, Progressives also fully control America's social institutions - academia, the media, and the arts and entertainment industry - and these are fully on-board with an apparent Popular Rejectionism, by which is proclaimed the absolute illegitimacy of any Republican or conservative challenge to Democrat control of government.