By Our Revolutions head says, Democrats have lost their souls. She will make them find religion.

[Jim Lane]

138. Solid blue districts is precisely where primaries make the most sense

You'll find this thread littered with dire warnings that a primary victory by a progressive Democrat might produce a nominee who's too progressive to win the general election. That's obviously far more of a concern in some places than in others.

For example, I've heard that there are primary challenges from the left being mounted against Senator Joe Manchin (D-WV) and to Congressmember Nancy Pelosi (D-CA). Without knowing much about either race, my guess is that the incumbents, both personally popular, will win renomination easily. But suppose they lose -- what will happen? West Virginia has, alas, become a red state, which went heavily for Trump. Manchin, if renominated, may win re-election because of his personal popularity, but a more progressive Democrat would presumably be the underdog in November.

Pelosi's district, by contrast, is as solid blue as they come. It's located entirely within the city of San Francisco. Its Cook PVI rating is D+37, meaning it averages 37 percentage points more Democratic than the nation as a whole. In the last midterm, 2014, Pelosi beat her Republican opponent by 83-17. Any Democrat who replaces her will also win in a walk.

So, no, I don't find it odd that the people you deride "only seem to want to unseat Dems in solid blue districts". Those are precisely the districts where a primary fight can't possibly cost the Democrats a seat.

The difficult questions come in more competitive districts. There, primary voters who are dissatisfied with the conservatism of an incumbent Democrat have to consider the benefit of replacing him or her with someone better, versus the danger that the challenger would lose the general election to the Republican. Allow me to offend the zealots on both sides by saying that there's no one-size-fits-all answer to that question.