“The first paper”:http://papers.ssrn.com/sol3/papers.cfm?abstract_id=1674091 is from Eric McGhee, Seth Masket, Boris Shor, and Nolan McCarty:
bq. Many supporters of political reform advocate opening party nominations to non-members as a way of increasing the number of moderate elected officials. This presumes that the composition of the primary electorate is, in fact, a significant cause of polarization, an idea that has rarely been tested empirically. We marry a unique new data set of state legislator ideal points to a detailed accounting of primary systems to gauge the effect of primary systems on polarization. The results of this analysis suggest that the openness of a primary election has little effect, if any, on the partisanship of the politicians it produces. We speculate on why the effect is so inconsistent and weak, and discuss the implications of our study for the theoretical literature on parties in American political life.
See also my “earlier”:https://themonkeycage.org/2010/03/will_the_toptwo_primary_end_po.html “posts”:https://themonkeycage.org/2010/03/more_on_the_toptwo_primary.html on Eric’s research as well as Seth’s “post”:http://enikrising.blogspot.com/2010/09/do-more-open-primaries-lead-to-less.html on this paper.
The second is a “newly published article”:http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=7890664&fulltextType=RA&fileId=S0898588X10000064 (gated) by Stephen Ansolabehere, John Mark Hansen, Shigeo Hirano and James M. Snyder:
bq. This article offers a first-ever comprehensive empirical assessment of a key Progressive reform, the direct primary, and its impact on competition in American elections. We begin with a review of the problems Progressives diagnosed in the American electoral system and reasons to expect the direct primary to be a pro-competitive, democratizing reform. We then consider prior research into the direct primary and electoral contestation and describe the database of primary and general election outcomes that we have constructed to trace competition in primaries for federal and statewide offices. Finally, we examine the historical trajectory of competition in primary elections, starting with the first decades after the introduction of the reform and then the succeeding decades.
bq. Consistent with the hopes of reformers, we find primary elections indeed provided a forum for contestation for federal and statewide elections. Although primaries were never broadly competitive, even at the outset, they accounted for about a third of the serious electoral tests faced by statewide officeholders and about a fifth faced by U.S. representatives. The role of primaries as a venue for robust contestation, however, was short-lived, as the competitiveness of federal and statewide primaries decreased sharply starting in the 1940s. The last section of this article explores whether two recent developments in American elections—the extension of two-party competition and the rise in the value of incumbency—conspired to temper the contribution of direct primaries to electoral competition.
“Here”:http://www.columbia.edu/~sh145/papers/index.html is more related research on primaries from Ansolabehere, Hansen, Hirano, and Snyder.