Barack Obama, a Democrat and America's first black president, was re-elected for a second term in November 2012 after a bitterly-fought campaign against Republican challenger Mitt Romney.
The Democrats kept control of the Senate and the Republicans remained in control of the House of Representatives, leading to political gridlock in Congress on the budget in late 2013.
The campaign focused on the ailing US economy. In his inaugural speech in January 2013, Mr Obama called on Democrats and Republicans to work together to sustain the country's fragile economic recovery. He also pledged an end to "ten years of war", signalling the departure of US troops from Afghanistan in 2014.