Publication of Hillary Clinton's new book, "Hard Choices," along with her many coming public appearances has sparked renewed speculation that the former secretary of state will seek the presidency again in 2016.
No one has been more active in flogging that speculation -- and in stressing Clinton's potential obstacles -- than Karl Rove, President George W. Bush's political "brain" who is now both a Fox News analyst and an adviser to a firm that produces Republican political ads.
Despite the partisan intent of Rove's comments on television and in his weekly Wall Street Journal column, he makes some valid points. Clinton's health will be an issue, especially if she displays any symptoms of the 2012 concussion that briefly hospitalized her. Likewise, her record as secretary of state, including the Benghazi chapter, will be a focus.
Rove, who regards himself as a historian as well as a political operative, also was on firm ground when he wrote recently that one of Clinton's biggest handicaps is that "it's tough for a party to win a third White House term."
Every party wears out its welcome, as Rove well knows from the GOP's 2008 defeat after Bush's two terms.
Since 1900, incumbent parties have won more than two White House terms on four occasions: William Howard Taft in 1908, Herbert Hoover in 1928, George H.W. Bush in 1988 and the 20-year Democratic tenure of Franklin D. Roosevelt and Harry S. Truman.
But that summary doesn't tell the whole story. Four of the five elections since World War II in which a party failed to win a third term were extremely close and could easily have gone the other way.
In 1960, Republican Vice President Richard Nixon sought to build on Dwight D. Eisenhower's two terms. He lost to John F. Kennedy, but the popular vote margin was just 112,827 votes. Kennedy might have failed to win an electoral majority, throwing the election into the House of Representatives, had he lost Texas and Illinois, where many Republicans accused Democratic machines of stealing the election.
Eight years later, Nixon won narrowly, preventing the Democrats from adding a third term to the two served by Kennedy and Lyndon B. Johnson. Their nominee, Hubert Humphrey, was closing fast and some allies still think he would have won if he or Johnson had disclosed what they considered improper interference in Vietnam peace talks by a Nixon backer, Anna Chennault.
In 1976, Jimmy Carter ended eight years of GOP rule by narrowly defeating President Gerald Ford, who became the only nonelected president when scandals forced both Nixon and Vice President Spiro Agnew to resign. Though Carter's popular margin was more than 1.7 million votes, a switch of fewer than 10,000 in Ohio and Hawaii would have given Ford an electoral majority.
Most analysts thought Ford would have won if he had not pardoned Nixon or had not claimed in a debate that Poland was free of Communist domination.
The fourth example came in 2000, when Texas Gov. George W. Bush defeated Vice President Al Gore in the closest modern election, 271-266 in the Electoral College vote. Gore had a 500,000-vote popular majority, but Bush won when the Supreme Court halted a recount in Florida, securing his 527-vote margin in that state, despite considerable controversy.
Gore was running to succeed Bill Clinton, whose popularity was high amid continuing economic growth. But he ran a poor campaign, including an odd debate performance in which he groaned and sighed audibly after Bush's answers and a reluctance to use Clinton more in states where his popularity might have enabled Gore to win.
If Clinton runs in 2016, her success will depend on her ability to avoid mistakes and on whether Republicans nominate someone whose personal appeal can surmount the GOP's current negative image and the demographic changes that favor the Democrats.
That outcome is neither foretold nor guaranteed by history.
Contact Carl P. Leubsdorf at email@example.com.