Ezra Klein writing for Vox:

There is a deep pull in political punditry toward asserting symmetry between the two political parties — whatever sins one party is guilty of, surely the other party is no better. But this was a week in which the pretense of symmetry between the modern Democratic and Republican parties fell away.

The Democratic Party is acting like the political parties we have traditionally known in American politics: It is backing familiar politicians with deep institutional ties and, amidst divided government, nominating compromise figures with the potential for bipartisan appeal.

The Republican Party, however, is moving in a different and worrying direction: It is nominating an inexperienced demagogue whose appeal is precisely that he has no institutional ties, and it is refusing to even consider compromise with the sitting president.