Richard Briffault has posted this draft on SSRN (forthcoming, The Best Candidate: Presidential Nomination in Polarized Times (Eugene D. Mazo and Michael R. Dimino, eds., Cambridge Univ. Press 2020)). Here is the abstract:

The Constitution says nothing about the presidential nominating process and has had little direct role in its evolution from congressional caucuses to party national conventions to our current primary-dominated system. Yet, constitutional law is a factor in empowering and constraining the principal actors in the nomination process and in shaping the framework for potential future changes.

The constitutional law of the presidential nomination process operates along two axes: government-party, and state-national. The government-party dimension focuses on the tension between the states and the federal government in writing the rules for and administering the electoral process – which may include the primary elections that determine the nominees of the political parties – and the right of the parties to determine how to pick their nominees. Doctrinally, this involves Supreme Court’s efforts to reconcile the power of the states to write the rules for state-run elections, including the primary elections that decide party nominations, with the freedom of political association guaranteed to the parties under the First Amendment.

This government-party axis affects all nominations for state and federal office. Presidential nominations, however, are distinct. For most elections, federal as well as state, most of the rules are determined by state law. But presidential nominations involve a national-level party decision for a nation-wide office. As a result, national party rules and federal laws factor into shaping the nomination process and add the possibility of conflicts between national- and state-level rules to the more common government-party tensions. Key Supreme Court rulings have held that national party rules and the decisions of the national party conventions take precedence over conflicting state laws and state party decisions. To date, Congress has played a minimal role in this area, and its authority to regulate the nomination process has been contested, but its powers need to be understood if Congress is to be involved in reforming this process.

The chapter concludes by suggesting that although the multiplicity of constitutionally-empowered actors may be – and has been – a source of conflict and complexity in the presidential nomination process, it may also be a strength. By permitting so many avenues for change, the constitutional framework creates multiple openings for reform.