No matter who is elected president, the doctrine embraced by President Bush will be retooled at the very least or possibly even tossed out entirely.
Defining the "Bush doctrine" has been open to debate, but it essentially boils down to dealing pre-emptively with emerging threats.
That was the argument Bush used to invade Iraq, an argument that proved questionable when weapons inspectors hunting for hidden caches of nuclear, chemical and biological weapons came up empty-handed.
That invasion was at the heart of the Bush doctrine. It has colored everything the president has done in the foreign policy world, and it will color everything the next president does.
Barack Obama has made much of his opposition to the war from the beginning, a war that John McCain supported. The two's views remain starkly different.
Obama opposed the surge of more than 30,000 troops into Iraq and still believes that it failed in its goal to produce a political solution.
Obama says he believes that all troops can be pulled out within a 16-month period after the election, although he would keep a residual force in Iraq and in the region to conduct targeted counter-terrorism missions against al Qaeda in Iraq and to protect American diplomatic and civilian personnel. Obama has never said how large a force would be needed. He is opposed to permanent bases.
McCain was a strong critic of the early strategy in Iraq but was a vocal supporter of the troop surge. Because of the surge's success in bringing greater security to Iraq, McCain does not want a timetable for withdrawal, preferring a "conditions-based" approach.
In a speech earlier this year, McCain said, "I intend to win the war and trust in the proven judgment of our commanders there and the courage and selflessness of the Americans they have the honor to command. The costs in lives and treasure we would incur would we fail in Iraq will be far greater than the heartbreaking losses we have suffered to date. I will not allow that to happen."
Both candidates want more troops in Afghanistan after a dramatic increase in violence there in the last year. Both know that in order to get those troops without increasing deployment time for individual soldiers and Marines, there will have to be an additional drawdown of American forces in Iraq.
McCain has suggested that NATO fill the gap, but there has been little appetite for that among U.S. allies.
Because Obama has advocated an immediate drawdown in Iraq, troops could be more readily available for a shift to Afghanistan under an Obama presidency.
If there is another Sept. 11, 2001, plot being hatched, it is almost certainly being planned in Pakistan's lawless tribal areas.
The subject of Pakistan has brought some of the most heated debate between the two men, but if you look beyond the verbal fireworks there is not a great deal of difference between the positions of McCain and Obama -- or, for that matter, Bush.
McCain ridiculed Obama for saying he would go after high-value al Qaeda targets along Pakistan's border, whether Pakistan approved or not. McCain would go after them as well; he just wouldn't talk about it in public. Earlier this year Bush signed a secret order allowing raids into Pakistan, and there has been a marked increase in activity along the border.
Both men vowed to go after Osama bin Laden until he is brought to justice. That is what Bush said as well, although many of the assets that were needed to do that were moved to Iraq. McCain and Obama say Afghanistan will once again be a primary focus.
President Bush has only recently allowed dialogue with Iran, which will likely continue with McCain or Obama. But the two men differ on whom they would talk to.
McCain does not support direct talks with Iranian leadership without pre-conditions, saying on "Fox News Sunday," "The question is, are you going to have direct talks, and does that enhance the prestige of the president of Iran, who said all these things about us, and has announced his country's continued distinction to the extinction of the state of Israel, or does it reach a successful conclusion? That's the question you have to ask when you talk about face-to-face talks."
Obama supports talks with Iranian leaders, saying that he believes in a carrot-and-stick approach and that he would move forward aggressively with dialogue and diplomacy while still supporting sanctions.
Neither of the men has ruled out military action as a last option if diplomacy fails or the threat of nuclear weapons is imminent.
On North Korea
Both McCain and Obama support continued diplomatic efforts with North Korea, but McCain opposed removing North Korea from the list of state sponsors of terrorism. Obama supported it.
McCain also rules out talks with North Korean leaders without preconditions. Obama, as he does in Iran, supports it saying, "This notion by not talking to people we are punishing them has not worked. It has not worked in Iran. It has not worked in North Korea. In each instance, our efforts of isolation have actually accelerated their efforts to get nuclear weapons."
An Evolving Doctrine
Whatever foreign policy the candidates are articulating now, it is almost certain to change because of events and the natural evolution of ideas.
Candidate George Bush espoused quite a different view of the world than he has as president. For Bush, it was 9/11 that necessarily changed his worldview.
For Obama and McCain, there is bound to be an unforeseen event that will change their views as well.