James Knox Polk ( /ˈpoʊk/ "poke"; November 2, 1795 – June 15, 1849) was the 11th President of the United States (1845–1849). Polk was born in Mecklenburg County, North Carolina. He later lived in and represented Tennessee. A Democrat, Polk served as the 17th Speaker of the House of Representatives (1835–1839) and Governor of Tennessee (1839–1841). Polk was the surprise (dark horse) candidate for president in 1844, defeating Henry Clay of the rival Whig Party by promising to annex Texas. Polk was a leader of Jacksonian Democracy during the Second Party System.

Polk was the last strong pre–Civil War president, and he is the earliest of whom there are surviving photographs taken during a term in office. He is noted for his foreign policy successes. He threatened war with Britain over the issue of which nation owned the Oregon Country, then backed away and split the ownership of the region with Britain. When Mexico rejected American annexation of Texas, Polk led the nation to a sweeping victory in the Mexican-American War, which gave the United States most of its present Southwest. He secured passage of the Walker tariff of 1846, which had low rates that pleased his native South, and he established a treasury system that lasted until 1913.

Dark horse is a term used to describe a little-known person or thing that emerges to prominence, especially in a competition of some sort or a contestant that seems unlikely to succeed.

The term began as horse racing parlance. A dark horse is a race horse that is not known to gamblers and thus is difficult to place betting odds on.

The earliest-known use of the phrase 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 term has been used politically in such countries as Peru, Philippines and United States.

Politically, the term reached America in the nineteenth century when it was first applied to James K. Polk, a relatively unknown Tennessee Democrat who won the Democratic Party's 1844 presidential nomination over a host of better-known candidates. Polk won the nomination on the ninth ballot, and went on to win the presidential election.

Mexican Americans are Americans of Mexican descent. As of July 2009, Mexican Americans make up 10.3% of the United States' population with over 31,689,000 Americans listed as of Mexican ancestry. Mexican Americans comprise 66% of all Hispanics and Latinos in the United States. The United States is home to the second largest Mexican community in the world second only to Mexico itself comprising nearly 22% of the entire Mexican origin population of the world. Canada is a distant third with a Mexican origin population of 37,000 as of 2001 although increasing to 61,505 as of 2006. In addition, as of 2008 there were approximately 7,000,000 undocumented Mexicans living in the United States which if included in the count would increase the US share to over 28% of the world's Mexican origin population (Note that some of the undocumented would be captured in the US Census count depending on their willingness to provide information). Over 60% of all Mexican Americans reside in the states of California and Texas. Most Mexican Americans are the descendants of the Indigenous peoples of Mexico and/or Europeans, especially Spaniards.