The 2016 Democratic presidential nominee–whomever it turns out to be–will face resistance from recent history. Since the end of the 20-year Democratic run in the White House that began with Franklin D. Roosevelt and ended with Harry Truman, there have been six occasions when either major party could have extended its control of the White House to three terms. But this has happened only once: when Republican George H.W. Bush in 1988 won what some have called Ronald Reagan’s third term.

As for the other five times: In 1960, eight years of Republican Dwight D. Eisenhower was followed by the election of Democrat John F. Kennedy. In 1968, after eight years of Democrats–Kennedy and Lyndon B. Johnson–Republican Richard M. Nixon was elected. In 1976, after eight years of a GOP White House–Nixon and Gerald R. Ford–Democrat Jimmy Carter won the presidency. In 2000, after eight years of Democrat Bill Clinton, the winner was a Republican: George W. Bush. And in 2008, after eight years of Mr. Bush, Democrat Barack Obamawas elected.

Clearly, “time for a change” sentiment seems to kick in after one party has occupied the Oval Office for two terms. Yet many of these potential “third term” elections have been close. Mr. Carter won the popular vote in 1976 by just 2 percentage points; Kennedy in 1960 and Nixon in 1968 triumphed by less than 1 point. In 2000 Mr. Bush famously lost the popular vote to Democrat Al Gore but narrowly won the all-important electoral vote.