Kevin D. Williamson has multiple points to make. This is the one that I particularly agree with.
Fourth, and related: The Democrats don’t seem to understand what it is they are really fighting, which, in no small part, is not the Republicans but the constitutional architecture of the United States. The United States is, as the name suggests, a union of states, which have interests, powers, and characters of their own. They are not administrative subdivisions of the federal government. All that talk about winning x percent of the “national House vote” or the “national Senate vote” — neither of which, you know, exists — is a backhanded way of getting at the fact that they do not like how our governments are organized, and that they would prefer a more unitary national government under which the states are so subordinated as to be effectively inconsequential. They complain that, under President Trump, “the Constitution is hanging by a thread” — but they don’t really much care for the actual order established by that Constitution, and certainly not for the limitations it puts on government power through the Bill of Rights and other impediments to étatism.
I know people who will argue that the "national House vote" does indeed exist. And they probably are voting with national outcomes in mind. But all politics is local and voters can only vote for the candidates on their own ballot. And as much as people give Congress — as an overall body — abysmally low grades, they tend to give their own representatives a much higher grade.
That's why Congress has such a low rate of turnover: everyone hates everyone else's representatives, but loves their own. And that's why I don't think that a "national House vote" truly exists. I can imagine a world in which a national vote does exist, but it's a different world than this one, with a different electoral system.