Historically, Americans have tended to vote for a President who is younger than his predecessor, sometimes dramatically so, as with John F. Kennedy after Dwight D. Eisenhower (27 years difference); as with Bill Clinton after George H. W. Bush (22 years difference); as with Barack Obama after George W. Bush (15 years difference); and as with Jimmy Carter after Gerald Ford (11 years difference).
In fact, only the following Presidents were older than their predecessors: William Henry Harrison, Zachary Taylor, James Buchanan, Chester Alan Arthur, Benjamin Harrison, William Howard Taft, Woodrow Wilson, Lyndon B. Johnson, and Ronald Reagan. And only W. H. Harrison, Taylor, Buchanan, Lyndon B. Johnson, and Reagan were five years or more older than their predecessors.
But now, in 2016, we are likely, almost certainly, to elect a President who will be substantially older than Barack Obama. This includes Joe Biden, Bernie Sanders,Jim Webb, Hillary Clinton, Elizabeth Warren, Jeb Bush, John Kasich, Carly Fiorina, Dr. Benjamin Carson, Rick Perry, Rick Santorum, Lindsey Graham, Mike Pence, Rick Snyder, Jon Huntsman and Mike Huckabee, a total of 16 potential candidates.
The odds of a younger President than Barack Obama are quite low, including Chris Christie, Rand Paul, Andrew Cuomo, Martin O’Malley, Scott Walker, Marco Rubio, Bobby Jindal, and Ted Cruz, a total of 8 potential candidates.
This oddity makes one wonder if the younger generation (under 45) will be as motivated to vote, as they are, naturally, attracted to comparative youth, as John F. Kennedy, Jimmy Carter, Bill Clinton, and Barack Obama represented, when they were elected, and with the extra appeal of being, respectively, the first Catholic (JFK); the first two Southern governors (Carter and Clinton); and the first African American (Obama).