Dark horse

A dark horse is a previously lesser-known person, team or thing that emerges to prominence in a situation, especially in a competition involving multiple rivals, that is unlikely to succeed but has a fighting chance, unlike the underdog who is expected to lose.
The term comes from horse racing and horse betting jargon for any new but promising horse. It has since found usage mostly in other sports, sports betting, and sports journalism and to lesser extent in nascent business environments, such as experimental technology and startup companies.
The term began as horse racing parlance for a race horse that is unknown to gamblers and thus difficult to establish betting odds for.
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."
The concept has been used in political contexts in such countries as Iran, Philippines, Russia, Egypt, Finland, Canada, the United Kingdom, and the United States.
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.
Other successful dark horse candidates for the United States presidency include:
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.
In Peru, "dark horse" candidates who won include Alberto Fujimori, who defeated Mario Vargas Llosa in the 1990 election, and Pedro Castillo, a previously unknown elementary school teacher, who won the 2021 election. In the United Kingdom, Jeremy Corbyn was considered a "dark horse" candidate when he ran for the 2015 Labour Party leadership election; despite struggling to secure enough nominations from the Parliamentary Labour Party to stand as a candidate, he won the leadership in a landslide. In Venezuela, then-President of the National Assembly Juan Guaidó was described as "the accidental leader" of the Venezuelan opposition; he declared himself acting president in 2019, during the Venezuelan presidential crisis. In Turkey, Ekrem İmamoğlu was little-known before his victory in the 2019 Istanbul mayoral election. In Iran, Masoud Pezeshkian, a little-known "dark horse" candidate, was allowed to run by the Guardian Council and won a surprising victory in the second round of the 2024 Iranian presidential election.
The term has been used in sport to describe teams and athletes who unexpectedly outperformed their expectations in a competition. Examples include the Los Angeles Kings during the 2012 Stanley Cup playoffs (who placed 1st despite being an 8th-seed entry into the playoffs); Bulgaria at the 1994 FIFA World Cup; Croatia at the 1998 FIFA World Cup and 2018 FIFA World Cup (who placed 2nd despite being ranked 20th in the FIFA World Rankings), Morocco at the 2022 FIFA World Cup (who placed 4th despite being ranked 23rd in the FIFA World Rankings); and Turkey at the 2002 FIFA World Cup (who placed 3rd despite being ranked 31st in the FIFA World Rankings).