As the Republican race for the nomination heats up, IBTimes UK asks when does a candidate become too old to run for public office?
How old is too old?
The average age for an elected president is between 50-54. No president has ever been inaugurated older than 69.
The nature of a US presidential campaign is one of stamina. Candidates this time around entered the race in June 2011 on average - 18 months before the general election. To be president, a candidate must be up to the physical demands of travel, speech-making, hand-shaking and constant media coverage even before they get to the White House.
Of the five oldest presidents, two have died in office - Zachary Taylor and William Henry Harrison (the latter after just 31 days in office.) Both were in their late 60s.
Over the past few years there have been several examples of American politicians running for president who have been just as old. Republican candidate Ron Paul is 76 and, although highly unlikely, if he managed to win the nomination his first term would see him though the 80-year-old mark - the average life expectancy of the US.
Republican candidate John McCain was 72 when he lost the 2008 election and Newt Gingrich will be 69 by the time of the November elections.
Even the "younger" candidates this year, Mitt Romney and Rick Santorum, are 64 and 53 respectively.
Are these candidates too old?