Jon Chait hints at this, but it is worth saying that while any liberal will have to appreciate some elements of David Frum’s growing alienation from the conservative establishment it’s not at all clear to me that the heart of his criticism — that Republicans need to moderate in order to become electorally viable — is really true. The empirical evidence to me suggests that our default view about the relationship between ideology and electability ought to be one of nihilism — any challenger can win provided the economy is doing poorly, and any incumbent can get re-elected provided things are going allright. An important caveat to that is that our empirical data rests on the assumption that both parties are able to mount real nationwide campaigns.
I do think, however, that there are two senses in which moderation would be useful. One has to do with race. There’s obviously a lot of identity-driven voting happening, and right now African-Americans, Asians, and Hispanics are both disinclined to vote Republican relative to demographically similar white Anglos. Republicans either need to increase their appeal to non-whites or else drive up increasing levels of white solidarity voting to stay viable.
The other, more important sense, is that precisely because it’s the fundamentals that matter most to campaigns actually governing well makes a great deal of difference to political outcomes. The big problem with thinking that tax cuts cure all problems, in other words, isn’t that it’s unpopular it’s that tax cuts do not in fact cure all problems which makes it hard to govern effectively and avoid the sort of bad outcomes that lead to incumbent losses.