Renata Strause and Dan Tokaji have posted this draft on SSRN.  Here is the abstract:

Prepared for Symposium on “The Future of Campaign Finance Reform” hosted by the Duke Journal of Constitutional Law and Public Policy and Center on Law, Race, and Politics.

This article considers the evidence that should be collected and developed to support the next generation of campaign finance reform before the next Supreme Court. It discusses but ultimately sidesteps theoretical debates over rationales for reform, focusing instead on the practical questions likely to be faced by future policymakers, lawyers, and expert witnesses. Drilling down into the ample evidentiary record in McConnell v. Federal Election Commission, the article addresses the evidence that should be amassed by supporters of future regulation. This type of evidentiary record will be essential both in formulating the next generation of campaign finance reforms and in defending them in court. The article argues that, regardless of whether one favors an anti-corruption or egalitarian rationale for regulation, the evidentiary record should focus on conflicts of interest – in particular, on whether a reasonable legislator would feel pressure to act in way that is different from the preferences of her constituents or the public interest. This is something more than a showing of unequal access, but something less than a showing of actual influence on policymaking. In the near term, these suggestions are designed to help define a research agenda for qualitative and quantitative empirical researchers. In the long term, they offer a roadmap for legislators shaping and lawyers defending future regulations before a Supreme Court less reflexively antagonistic to reform than the current one.