It’s amazing what an obsession there is with the idea of the ‘moderate Republican’. There are a lot of establishment Democrats who sort of wish they had somewhere else to go in case the Sanders-Warren wing takes over the party, and a lot more not particularly politically savvy Democrats who keep thinking that a mythical ‘moderate Republican’ would be the scariest of all electoral opponents.
The issue is that there isn’t any such thing. So many policy areas these days are binaries: do you think we should take action on global warming? Should taxes on the wealthy go up or down? Should we regulate Wall Street more or less? Are you pro-choice or pro-life? On and on… what does a moderate mean in this situation? Someone with a mix of liberal and conservative positions on different ones of these policies? Any one deviation from right-wing orthodoxy is enough to disqualify you in Republican primary. Someone who tries to split the difference on a lot of things? Then you’re basically Hillary Clinton.
No Republican who doesn’t take hyper-conservative positions on every issue will ever be nominated on the Presidential level, and barely any can do so on any level. And even if / when by some miracle they do get nominated, such candidates can’t turn out the deranged Republican base.