Since the 1790s the USA has been run by two major political parties – and since its Civil War in the 1860s they have been the Republican and Democratic parties.

Minor or third political parties appear from time to time and generally promote policies that are eventually adopted by the two major parties – like the abolition of slavery, and measures against child labour, for example.

Since the adoption of the Constitution, 42 people have followed George Washington into the presidency. Most have been elected, although some – like Lyndon B Johnson after the Kennedy assassination – have moved up from the vice-presidential role.

Franklin D Roosevelt is the only man to win four elections, leading the USA through the twin perils of the Great Depression and World War Two. A two-term maximum was imposed after his death.

A popular myth has it that the taller presidential candidate wins the race for the White House – and between 1928 and 1968 that was the case. But George W Bush was shorter than both Al Gore, who he defeated in 2000, and John Kerry, who he beat in 2004, and Bill Clinton was the shorter candidate in 1992.

The 43rd and current president is George W Bush, inaugurated on 20 January 2001 to a first term and on 20 January 2005 to a second. His term expires at noon on 20 January 2009, after which he will be succeeded by the winning candidate of the 2008 presidential election.

You can bet on the next US president with William Hill.

• Post War US Presidential Election Results