The war in Iraq was the central issue in the last election but has dropped down many voters' list of priorities in 2008.
The situation on the ground in Iraq has improved for the US since the start of the "surge" in spring 2007, when 30,000 extra troops were sent to the country.
Attacks on troops and civilians are down, refugees have started coming back and there are hopes that life in the country may slowly be returning to normality.
More than a year after the surge began, a substantial proportion of Americans - some 44%, according to a Pew Research Center poll in June - think the military effort is going well.
The same poll suggests voters are divided over whether the US should withdraw its forces from Iraq, with 41% saying troops should stay in the country and 56% saying they should come home as soon as possible.
Democratic presidential candidate Barack Obama - who opposed the 2003 invasion, as well as the troop increase - has said he would start withdrawing combat troops immediately after taking office, with all forces out of combat operations within 16 months.
However, he has said he would leave a residual force for US mission protection, training Iraqi forces and fighting against al-Qaeda.
If the news from Iraq continues to improve, he may come under pressure to come up with a plan to win the Iraq war, as well as reduce troop numbers.
Republican presidential candidate John McCain has accused the Democrats of seeking to reverse the positive effects of the surge by withdrawing troops prematurely.
In one much-publicised statement during campaigning for the primary elections, he said that there could still be a US military presence in Iraq in 100 years' time.
However, he said in May 2008 that that under his presidency most US forces would be withdrawn by 2013, as by this time Iraq would have become a "functioning democracy".
This has led some commentators to suggest that the practical differences between "phased withdrawal" and "maintaining troop levels" are fairly cosmetic.
Most people in the US believe that troops will remain in Iraq for several years, whichever party wins the White House.