When Hoffman and Howard measure success, they do it from the view of the president. But a 12 percent difference between first- and second-term legislative success doesn't seem enough to warrant a term like "curse" – or determine whether second-term presidents fail or just falter.
One interesting take on the issue comes not from a professional historian but an Indiana real estate agent, Alfred Zacher, whose lifelong passion has been the study of second terms. His self-published book tries to catalog whether presidential second terms were "successful," "troubled," or "failed." He counts only five failures: Grant, Cleveland, Johnson, Nixon, and Bush.
The problems that recurrently surface for presidents – whether in their first term or second – seem to be the same four:
Unpopular wars. Truman in Korea, Johnson and Nixon in Vietnam, and Bush in Iraq – their second terms all included war or military action Americans disliked.
Bad economies. The 1987 stock market crash hurt Reagan, and the broader economic collapse in 2008 marred Bush's legacy. But the 1873 and 1893 recessions in Grant's and Cleveland's respective second terms were enormous setbacks, too.
Personal scandal or corruption. The Monica Lewinsky affair led to Clinton's impeachment, and Nixon's ordering of the Watergate coverup resulted in his impeachment and resignation.
Grant was hobbled by the appointment of a Treasury secretary who turned out to be a crook. Reagan eventually took the blame for Iran-contra, though it's unclear how sharply he had focused on the issue.
Jefferson's problems with one member of his administration may have been in a class of their own: His first-term vice president, Aaron Burr, killed Alexander Hamilton in a duel and later, after being jettisoned from the administration, was tried for treason for supposedly fomenting revolution on the Western frontier. The controversies surrounding Burr, and Jefferson's handling of them, no doubt affected his popularity.