Nate Silver has a fun piece up this morning about potential late entries in the Republican WH 2012 field, and how they might fit into the current group.
I'm not sure how helpful it really is, however. Mainly, I'm not at all convinced that Silver's central conceit of a two by two grid with an ideological axis and an establishment/insurgent axis is a useful way of thinking about the nomination process. On the ideological side, it's not clear how many important individuals and groups within the party are thinking in terms of left/right (or, I suppose, right/very right) rather than about specific policy areas of concern. That is, what really matters isn't so much whether a candidate is too moderate, but whether the abortion people, the tax people, and so on find the candidate acceptable or not.
I'm also not convinced that an establishment/insurgent vocabulary really captures the relationship of the various groups within the GOP, or the appeal of the candidates. What exactly is an establishment-friendly or insurgent candidacy? If it's just rhetoric, then we're probably talking about appeal to larger electorates in next year's primaries, but no candidate is going to get there without considerable support from organized groups within the party. If it's appeal to particular groups, I don't think the groups really exist on an establishment/insurgent spectrum. Indeed, if you're talking about groups, it's probably just better to think about groups, specifically and in general, without worrying about whether they are "establishment" or their ideological placement.
Not sure if I'm being clear here...what I mean is that it's not so important how conservative, say, Rudy Giuliani is; what matters is that social conservatives certainly would strongly oppose him, and that those groups have an effective veto on the nomination. Similarly, what matters is whether those groups would attempt to veto Mitt Romney, or if they find him acceptable. And then to remember that there are multiple specific groups (within the broad category of social conservatives) and they might disagree with one another, and that the nomination fight might be, in part, a fight between those groups for who gets to speak for that particular GOP constituency. A fight which might or might not be usefully characterized as establishment/insurgent, and might or might not have any relationship at all to similar fights within, say, anti-tax GOP organizations and individuals.