to make Obama, a Democrat, a "one-term president".

In the same year, Obama himself told Diane Sawyer of ABC News: "I'd rather be a really good one-term president than a mediocre two-term president."

Defenders of Bush, the 41st president, put him in the former category.

His time in office coincided with the fall of the Berlin Wall and his popularity soared in the wake of the first Gulf War.

However, a protracted economic recession on his watch saw him break a pledge not to raise taxes, provoking fierce hostility from within his own Republican party. With Ross Perot, a third-party candidate, splitting the vote in the 1992 election, Bush's attempts to win re-election were thwarted by the charismatic Bill Clinton.

Larry Sabato, director of the Center for Politics at the University of Virginia,believes Bush was a victim both of timing and the US's system of fixed-term presidencies.

"Margaret Thatcher could call an election to capitalise on the Falklands War, but George HW Bush couldn't do that to capitalise on the first Persian Gulf War," Sabato says.

"If he could have done that, he would have won."

Image copyright Getty Images Image caption George and Barbara Bush in the 1960s

George HW Bush: a political life

1966: Wins seat in House of Representatives

1971: Nixon installs him as UN ambassador

1974: Heads newly established mission in Beijing

1976: Ford makes him CIA director

1981-1989: Ronald Reagan's vice-president

1989-1993: President of the US; leads US into first Gulf War; copes with collapse of communism in Eastern Bloc

For Sabato, recent one-term presidents have been the victim more of adverse circumstances than of their