I've been pointing to the reluctance of Democratic Senate candidates to run on many liberal issues; Rachel Weiner has a WaPo story today about how poorly some liberal candidates have been doing in House primaries.
Of course, there's no shortage of stories about conservative victories in Republican House and Senate primaries. One can take this too far; it's not even close to true that the more conservative candidate regularly wins Democratic primaries. But still, there does certainly seem to be a difference. I've talked about the consequences...I think on balance it does lose seats for Republicans, but make them more reliable votes when they do win. But the question is: what's the explanation for the difference?
Note: I don't think the same is true for presidential nominations, for whatever that's worth.