In the broadest sense, the book is meant to contribute to our understanding of how American democracy operates. It is guided by and adds to the scholarly literatures on survey research, public opinion, political parties, congressional elections, political parties, and the presidency. The idea for it emerged from research for an earlier book on the public’s reaction to President George W. Bush’s performance and policies, particularly regarding the Iraq War. I suspected that the growing unpopularity of Bush and the war during his second term might have inflicted collateral damage on the Republican Party and found evidence that it did. This raised the question of whether performance ratings of other presidents affected their party’s public standing, and the answer, after some additional research was a clear “yes.”While pursuing that question, I discovered the wide variety of ways in which opinion surveys had, over the postwar period, sought to measure popular reactions to presidents and their parties. These studies produced a remarkably rich trove of data for examining myriad ways in which modern presidents and presidential candidates have influenced how people view their parties. I reported analyses of some of these data in a series of papers and journal articles but eventually decided that only a book offered the latitude adequate to the data and subject. I aimed to finish book with the completion of the Obama administration, but as I was wrapping it up, Trump was elected, and the question of how such a bizarrely unorthodox president might alter the relationships I had been investigating was too intriguing to ignore, so I added a section on his campaign and early presidency. I continue to collect data on Trump and the Republican Party and will be updating my analyses of his administration in future work.