In 1968, Hubert Humphrey, the sitting vice president, was nominated as the presidential candidate for the Democratic Party without campaigning in a single primary. Fast-forward to 2016, when Donald Trump, a clear party outsider, emerged as the winner of the Republican nomination, despite the preferences of many, if not most, Republican elites. How could it be that we have gone from a nominating system of party elite control to one in which a distant outsider can win? In Caitlin E. Jewitt’s recent book, The Primary Rules: Parties, Voters, and Presidential Nominations, she convincingly argues that at least part of this answer comes down to changes in the rules of how nominees are selected.

The idea that the rules matter in determining election outcomes is hardly new territory in political science. What Jewitt brings to the table is a uniquely comprehensive and detailed examination of changes in the nomination rules of both parties over nearly 50 years, not to mention systematic analyses of their effects. She begins by walking us through a host of national party rule changes and reform commissions. The point is clear: while the bulk of the attention in the literature has fallen on the McGovern-Fraser Commission, it was only the start, with significant changes occurring before every nomination—changes in response to the most recent nomination o