The term began as horse racing parlance for a race horse that is unknown to gamblers and thus difficult to place betting odds on.
The first known mention of the concept is in Benjamin Disraeli's novel The Young Duke (1831). Disraeli's protagonist, the Duke of St. James, attends a horse race with a surprise finish: "A dark horse which had never been thought of, and which the careless St. James had never even observed in the list, rushed past the grandstand in sweeping triumph."
In the political arena
Politically, the concept came to the United States in the nineteenth century when it was first applied to James K. Polk, a relatively unknown Tennessee politician who won the Democratic Party's 1844 presidential nomination over a host of better-known candidates. Polk won the nomination on the ninth ballot at his party's national nominating convention, and went on to become the country's eleventh president.
- Franklin Pierce, chosen as the Democratic nominee and later elected the fourteenth president in 1852.
- Abraham Lincoln, chosen as the Republican nominee and elected as the sixteenth president in 1860.
- Rutherford B. Hayes, elected the nineteenth president in 1876.
- James A. Garfield, elected the twentieth president in 1880.
- Warren G. Harding, elected the twenty-ninth president in 1920 after his surprise nomination.
- Jimmy Carter, elected the thirty-ninth president in 1976; in the beginning of that same year, Carter was relatively unknown outside his home state of Georgia but went on to win the nomination over rivals with more national prominence.
- Donald Trump, a real estate investor and television personality, who defeated 15 established rivals for the Republican nomination before beating former Secretary of State Hillary Clinton in the election. Trump had never held political office prior to his presidency, but had been running or planning to run for President since 1999, with little interruption.
Perhaps the two most famous unsuccessful dark horse presidential candidates in American history are Democrat William Jennings Bryan, a three-term congressman from Nebraska nominated on the fifth ballot after impressing the 1896 Democratic National Convention with his famous Cross of Gold speech (Bryan would go on to receive the Democratic presidential nomination twice more and serve as United States Secretary of State), and Republican businessman Wendell Willkie, who was nominated on the sixth ballot at the 1940 Republican National Convention despite never having previously held government office and having only joined the party in 1939.
Outside of the United States, the dark horse status also attributed to Alberto Fujimori, who rose to the Presidency in Peru. In Nigeria, Goodluck Jonathan can be referred as a dark horse, as he was the first president from the historically marginalized Niger Delta region, and he also rose through three political offices (from deputy governor of Bayelsa State to governor, from governor to vice-president, and from vice-president to president) through unusual circumstances. In Finland, Lauri Kristian Relander was elected President as a dark horse in 1925, his party naming him as its candidate only after the people had voted for presidential electors. A dark horse presidency in Finland remained possible, and sometimes speculated upon, until the electoral system was changed to a direct personal vote in 1987.
Several government ministers, who were appointed to the third cabinet of Russian prime minister Dimitri Medvedev on 21 May 2012, were also described as "dark horses" for lacking experience, such as Olga Golodets, Vladimir Medinsky and Alexander Novak. Some of the candidates for the presidency of Iran in 2013 were labelled as dark horse, including Mohammad Baqer Qalibaf, Mohsen Rezai, Mostafa Pourmohammadi, Mohammad Saeedikia and Mohammad Gharazi. In the United Kingdom, Jeremy Corbyn, who won the 2015 Labour Party leadership election despite struggling to secure enough nominations from the Parliamentary Labour Party to stand as a candidate, has also been described as a dark horse.
Use in music, television, and film
In addition, surprising or unlikely nominations for such prizes as the Academy Award (awarded by the Academy of Motion Picture Arts and Sciences) are referred to as dark horses.
Guitarist and singer-songwriter George Harrison was nicknamed the "dark horse" of The Beatles, as his visibility as a songwriter and vocalist increased later in the Beatles' career, particularly on Abbey Road. Harrison went on to name his solo label Dark Horse Records and release both an album and a song named "Dark Horse."
The 24th chapter of Mark Helprin's novel Winter's Tale is called 'White Horse and Dark Horse,' referring to the character of Praeger de Pinto as an outlier candidate for the Mayor of New York City.
The first episode of the second season of Frisky Dingo is called "Behold a Dark Horse."
Dark horse is the name of a song recorded by American metalcore band The Ghost Inside.
The fourth largest comic book publisher is called Dark Horse Comics.
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