In American history, we have had only five Presidents who were 64 or older in office when inaugurated—Ronald Reagan, William Henry Harrison, James Buchanan, George H. W. Bush, and Zachary Taylor.
An additional five Presidents were ages 60-63 when inaugurated: Harry Truman, Gerald Ford, John Adams, Andrew Jackson, and Dwight D. Eisenhower, but Truman and Ford were not elected at that age, but instead succeeded to the Oval Office.
This means 33 of our 43 Presidents were younger than 60 when being inaugurated President, with 24 in their 50s, and 9 in their 40s, and with Grover Cleveland in his 40s for his first term, and 50s for his second nonconsecutive term. The nine Presidents in their forties were, at the time of inauguration: James K. Polk and James A. Garfield (49); Franklin Pierce (48); Grover Cleveland and Barack Obama (47); Ulysses S. Grant and Bill Clinton (46); John F. Kennedy (43); and Theodore Roosevelt (42).
But it is now likely that the next President will be in his or her 60s, or even 70s, at the time of taking the Presidential oath. There are a total of eight potential Republican nominees in their 60s–ranging from, at the time of inauguration as follows: Mitt Romney (69); Rick Perry (66); Dr. Benjamin Carson (65); John Kasich (64); Jeb Bush (63); Mike Huckabee, Rob Portman, and Lindsey Graham (61). Romney and Perry would reach the age of 70 during a first term, and Romney, Perry, Carson, Kasich and Bush would all be in their 70s in a second term.
Meanwhile, the Democrats have four potential Presidential nominees who will be in their seventies when they would take the oath of office—Jerry Brown (78); Bernie Sanders (75); Joe Biden (74); and Jim Webb (70). All four, plus Hillary Clinton (69) and Elizabeth Warren (67) would reach the 70s during a first term, and Mark Warner (62) would reach 70 as well in a second term.
So a total of eight Republicans and seven Democrats would be over 70, either at the time of the inauguration, or within the next four years after, or the next eight years after!
When one realizes that only Dwight D. Eisenhower (70) and Ronald Reagan (77) were actually in the Presidency past their 70th birthday, and Ike was only three months beyond 70, it is clear that we are likely to create new ground, since much of the talent pool is comparatively old, and from the “Baby Boomer” generation born from 1946 onward.
Of course, there are younger Presidential candidates or potential candidates–for the Republicans–Rick Santorum (58); Mike Pence (57); Rand Paul and Chris Christie (54); and in the 40s in 2016, the following: Scott Walker (49); Ted Cruz and Paul Ryan (46); Marco Rubio and Bobby Jindal (45), a total of nine other potential Presidents.
The Democrats have fewer alternatives: in the 50s in 2016 are: Andrew Cuomo (59); Amy Klobuchar (56); Martin O’Malley (54); and Kirsten Gillibrand (50). No one in their forties is seen as a potential Democratic nominee.
So we might end up with the oldest combination of Presidential candidates in American history, with Hillary Clinton and Mitt Romney being front runners for now, and both reaching 70 within months of taking the oath of office!