One thing I've realized it that the Democratic party is a machine. It rewards loyalty and waiting your turn. It punishes getting out of line and challenging incumbents.

Parts of the Republican party are too of course (hence Grassley) but it's been the target of several successful insurgencies. First the tea party and then Trump. Now it's turning into something completely different.. a cult of personalty for a dictator.

But the intact machine is the reason why the Democrats can not rise to the occasion. Their whole system is one designed to produce dour grey apparatchiks.