Whether it is President Lyndon Johnson calling Senator Abraham Ribicoff (D-CT) – “He told me what a low-life bastard I was and how I'd better get right with God” (Time, 7 August 1978) – or President Bill Clinton calling Senator Bob Kerrey (D-NE) – “If you want to bring this presidency down, then go ahead” (Stephanopoulos 1999, 176) – tales of presidents' pleas for lawmakers' support before crucial roll-call votes still reverberate across Washington. On both ends of Pennsylvania Avenue, these and comparable anecdotes are often said to reveal the essence of presidential power and exemplify its exertion on Capitol Hill. As John F. Kennedy noted, “The President must initiate policies and devise laws to meet the needs of the Nation. And he must be prepared to use all the resources of his office to…not let down those supporting his views on the floor” (17 January 1960).

But, of course, popular imagery of presidential power is one thing; systematic evidence is quite another. And by the latter standard, presidents' chances of securing legislative success have been appraised at less than the advertised value. Across various types of floor votes, including the most important ones, each president's fate has appeared to be largely (if not wholly) preset by the congressional delegation he confronts.