I'm going to continue by going back to David Karol's comment:
Relatedly, the fact that Scozzafava was nominated, not in a primary, but by local party leaders, while in keeping with the New York law for special elections, probably undermined her legitimacy once she was scrutinized. This is only one case, but as far as it goes it tends to undermine claims that party leaders would choose candidates more wisely than ordinary primary voters do.(I should repeat for those who didn't read the first part of this that I agree with Karol's broader comment; it's really good analysis, in my opinion, and I highly recommend it).
Ah, but now let me focus on his claim about "party leaders." As David should know, one thing that NY-23 certainly does not show is anything about party leaders in general. That's because party leaders turned out to be quite divided.
The key here is that one has to be careful about what a party leader is. The party networks literature points out that formal party organizations -- that's who nominated Scozzofava, the Official Republican Party Organization -- are only one piece of contemporary political parties. And, depending on time and place, the formal party organization may be very important -- or they may be marginal, peripheral organizations that have little to do with the "real" party (see, for example, Seth Masket's book, which describes exactly that situation in California). Other components of what I've called (e.g. here, with Casey Dominguez) the "expanded party" include candidate campaign organizations, the staffs of elected officials, campaign consultants, activists, party-aligned interest groups, and campaign, governing and communications professionals.
In normal primary elections, all of those party components have a chance to organize and try to influence the nomination. Moreover, everyone (or at least the experienced players) know how primaries "work" -- they know how to bring their particular resources to the table. For example, party-aligned interest groups (such as, on the Republican side, right-to-life activists, the NRA, etc.) know how to attempt to enforce discipline on candidates for the nomination. As I said in the first post in this series, I strongly suspect that had Scozzafava had to go through a primary election, she would have modified her views to make them more acceptable to more of these groups and individuals. That is, when David Karol suggests that party leaders "should have nominated someone with moderate leanings, but more conservative than Scozzafava," the likely solution was Scozzafava after a primary. There's nothing unusual about that; at the presidential level, there's a long history of candidates (Romney, Gephardt) who adjusted their abortion positions when they moved from a narrow constituency to a national nomination constituency; right now, watch Illinois Republican Senate candidate Mark Kirk, er, evolve as he moves to a statewide primary constituency.
So: in the case of NY-23, we had a variety of "party leaders" involved, only a few of whom were given any influence over the nomination. I don't know anything about how Republicans organize themselves in upstate New York these days, so I have no idea how important formal party functionaries are normally; it could be that they are quite influential normally, but it's also certainly possible that they are widely seen as irrelevant to everyday politics, and their control over nominations of candidates for the House in special elections is a massive anachronism. If the latter, they may have been ill-equipped to do the sorts of things (such as consultation with the real GOP players in the district) that might have either scared them off Scozzafava, or brought those other players on board.
Note too that there's a local vs. national component to this (although it's not all one-sided, if reports that the national party Congressional committee wanted Scozzafava). Again, in normal primary elections, these sorts of fights can play out properly, according to well-established rules and norms. But, and here's where I go back to David's formulation, these are not fights between "party leaders" on one side and "ordinary primary voters" on the other. Instead, these are fights between various different party leaders -- local formal party officials, local activists, local campaign and governing professionals, local interest groups, and also national formal party officials and staff, national activists, national campaigning and governing professionals, national interest groups, and national ideologues and whatever-Glenn-Beck-is. Ordinary primary voters may choose among those groups -- or, more likely, they ratify the winner of those fights (or the bargained consensus among the combatants).
So: NY-23 tells us nothing about the abilities in general of party leaders. It may, however, be a hint that Republican formal party officials in NY-23 are not central to the Republican Party of NY-23.