3. Lame-duck presidents have a hard time propelling their party’s candidate into the White House.

Analysts such as Megan McArdle of the Atlantic have made arguments along these lines. But a look at the historical record tells a different story.

Reagan helped George H.W. Bush win California — and the White House — in 1988. After Harry S. Truman ascended to the top job after FDR’s death, he earned his first complete term as president with a dramatic election in 1948, the fifth consecutive presidential election won by the Democratic Party. Calvin Coolidge, who became president after Warren G. Harding’s death — and then, after winning a new term on his own, refused to run for a second — helped Herbert Hoover succeed him. President Theodore Roosevelt appointed William Howard Taft his secretary of war, helping Taft win the presidency in 1908. President Ulysses S. Grant was succeeded (in a disputed election resolved by an electoral commission) by Rutherford B. Hayes in 1876. President Andrew Jackson was followed by Vice President Martin Van Buren after the 1836 election. And, of course, early on there was the 24-year stretch of three consecutive two-term Democratic presidents: Thomas Jefferson, James Madison and James Monroe.

Even in cases in which the incumbent party lost after winning two consecutive presidential elections, the defeats were often excruciatingly close. Richard M. Nixon lost only narrowly to John F. Kennedy in 1960; Gerald R. Ford lost a tight vote to Jimmy Carter even with Watergate and the Nixon pardon weighing him down; and Al Gore won the popular vote but lost the electoral college to George W. Bush after Bill Clinton’s two terms.