At a time when we have the oldest combination of Presidential candidates in history, with Donald Trump being past 70, and Hillary Clinton to be 69 in October, let’s take a look back at three Presidential candidates who lost, but were all younger than Theodore Roosevelt, our youngest President at 42 years and almost eleven months when he succeeded the assassinated President William McKinley in 1901; and these three Presidential candidates also, therefore, younger than John F. Kennedy, our youngest elected President, who took the oath at 43 years and almost eight months.
Our youngest Presidential nominee of a major party in history is William Jennings Bryan of Nebraska, a former Congressman, who ran as the Democratic nominee for President in 1896 and 1900, when he was younger than TR or JFK. Bryan was 36 and 40 when he ran his first two of three Presidential races, and had he won, he would have been inaugurated 15 days short of his 37th and 41st birthdays.
Our second youngest Presidential nominee was John C. Breckinridge of Kentucky, who was Vice President at age 36 under President James Buchanan from 1857-1861 but was actually 35 at the time of his election. He was the Southern Democratic nominee in 1860 at age 39 although he would have been 40 at the time of the inauguration, running against Republican Abraham Lincoln, Democrat Stephen Douglas, and Constitutional Union nominee John Bell. Breckinridge served in the US House before being Vice President, and later was part of the Confederate government and army during the Civil War, and later served in the US Senate from Kentucky.
Thomas E. Dewey of New York sought the Presidency for the first time in 1940, when he was 38, and serving as Manhattan County District Attorney, but was thought to be too young to be taken seriously. But in 1944, in his first of two Presidential campaigns, when New York Governor, he ran on the Republican Party line against Franklin D. Roosevelt, running for his fourth term as World War II was nearing its last months. Dewey would have been inaugurated about two months short of his 43rd birthday, had he won in 1944, making him about a month younger than TR when he became President.
Dewey was favored in his second round of Presidential candidacy in 1948, when he lost in an upset to Harry Truman, after all public opinion polls projected an easy win but at that point he would have been two months short of 47, at the time of inauguration.