The following are some of the key exchanges between Senator John McCain and Barack Obama, in their first debate:
IRAQ AND THE TROOP SURGE
McCain: This strategy has succeeded. And we are winning in Iraq. And we will come home with victory and with honour... Senator Obama said the surge could not work, said it would increase sectarian violence, said it was doomed to failure. Recently on a television program, he said it had exceeded our wildest expectations.
Obama: You talk about the surge. The war started in 2003, and at the time when the war started, you said it was going to be quick and easy. You said we knew where the weapons of mass destruction were. You were wrong. You said that we were going to be greeted as liberators. You were wrong. You said that there was no history of violence between Shia and Sunni. And you were wrong.
McCain: If we fail in Iraq, it encourages al-Qaeda. They would establish a base in Iraq. The consequences of defeat, which would result from his plan of withdrawal... would lead to the loss of all the fragile sacrifice that we've made of American blood and treasure, which grieves us all.
Obama: We've spent over $600bn so far, soon to be $1 trillion. We have lost over 4,000 lives. We have seen 30,000 wounded, and most importantly, from a strategic national security perspective, al-Qaeda is resurgent, stronger now than at any time since 2001. We took our eye off the ball.
IRAN, ISRAEL AND DIRECT DIPLOMACY
McCain: My reading of the threat from Iran is that if Iran acquires nuclear weapons, it is an existential threat to the State of Israel and to other countries in the region because the other countries in the region will feel compelling requirement to acquire nuclear weapons as well. Now we cannot allow a second Holocaust.
Obama: We cannot tolerate a nuclear Iran. It would be a game changer. Not only would it threaten Israel, a country that is our stalwart ally, but it would also create an environment in which you could set off an arms race in this Middle East.
McCain: What Senator Obama doesn't seem to understand is that if without precondition you sit down across the table from someone who has called Israel a 'stinking corpse', and wants to destroy that country and wipe it off the map, you legitimise those comments... it's just dangerous.
Obama: Senator McCain mentioned Henry Kissinger, who's one of his advisers, who, along with five recent secretaries of state, just said that we should meet with Iran - guess what - without precondition. This is one of your own advisors.
Obama: We had the highest fatalities among US troops this past year than at any time since 2002. And we are seeing a major offensive taking place - al-Qaeda and Taleban crossing the border and attacking our troops in a brazen fashion. They are feeling emboldened.
McCain: We've got a lot of work to do in Afghanistan. But I'm confident, now that General Petraeus is in the new position of command, that we will employ a strategy which not only means additional troops.
McCain: Now, the new president of Pakistan, Qadari [sic], has got his hands full... And the Pakistanis are going to have to understand that that bombing in the Marriott Hotel in Islamabad was a signal from the terrorists that they don't want that government to co-operate with us in combating the Taleban and jihadist elements.
Obama: The problem, John, with the strategy that's been pursued was that, for 10 years, we coddled [former President] Musharraf, we alienated the Pakistani population, because we were anti-democratic. We had a 20th Century mindset that basically said: 'Well, you know, he may be a dictator, but he's our dictator.'
Obama: Back in April, I warned the administration that you had Russian peacekeepers in Georgian territory. That made no sense whatsoever. And what we needed to do was replace them with international peacekeepers.
McCain: His first statement was: 'Both sides ought to show restraint.' Again, a little bit of naivete there. He doesn't understand Russia committed serious aggression against Georgia.
READINESS TO LEAD/EXPERIENCE
Obama: You're absolutely right that presidents have to be prudent in what they say. But, you know, coming from you, who, you know, in the past has threatened extinction for North Korea and, you know, sung songs about bombing Iran, I don't know, you know, how credible that is.
McCain: I'm not prepared to threaten it, as Senator Obama apparently wants to do, as he has said that he would announce military strikes in to Pakistan... Now, you don't do that. You don't say that out loud...
Obama: He [John McCain] even said the other day that he would not meet potentially with the prime minister of Spain, because he - you know, he wasn't sure whether they were aligned with us. I mean, Spain? Spain is a Nato ally.
McCain: I honestly don't believe that Senator Obama has the knowledge or experience and has made the wrong judgments in a number of areas... I don't think I need any on-the-job training. I'm ready to go at it right now.
McCain: Somehow in Washington today - and I'm afraid on Wall Street - greed is rewarded, excess is rewarded and corruption - or certainly failure to carry out our responsibility is rewarded.
Obama: We've had years in which the reigning economic ideology has been what's good for Wall Street, but not what's good for Main Street.
Obama: Senator McCain is proposing - and this is a fundamental difference between us - $300bn in tax cuts to some of the wealthiest corporations and individuals in the country, $300bn.
McCain: Now, Senator Obama... has asked for $932m of earmark pork-barrel spending. That kind of thing is not the way to rein in runaway spending in Washington DC.
McCain: We had an energy bill before the US Senate. It was festooned with Christmas tree ornaments. It had all kinds of breaks for the oil companies... I voted against it; Senator Obama voted for it.
Obama: It's just not true. And if we want to talk about oil company profits, under your tax plan, John - this is undeniable - oil companies would get an additional $4bn in tax breaks.
Obama: We have to... invest in alternative energy, solar, wind, bio diesel, making sure that we're developing the fuel-efficient cars of the future right here in the United States, in Ohio and Michigan, instead of Japan and South Korea.
McCain: Senator Obama says he's for nuclear, but he's against reprocessing and he's against storing... And we know that, if we drill off-shore and exploit a lot of these reserves, it will help, at least temporarily, relieve our energy requirements.