This is reflected in their attitudes about military action in Iraq. Clinton was for it in 2002 and was against it by 2007. Obama was always against what he called a "dumb war."
As for President George W. Bush's surge strategy, Clinton told Obama, in front of a surprised and dismayed Robert Gates, that her opposition to the surge was "political because she was facing him in the Iowa primary." Obama, according to Gates, merely conceded that opposition to the surge -- by whom? -- was political.
So perhaps it was not too surprising that Clinton told the Atlantic's Jeffrey Goldberg that "Hamas initiated this conflict" with Israel (a contrast with Obama's condemnation of violence on both sides), that Iran has no "right to enrichment" (which Obama is conceding in negotiations) and that Obama's refusal to aid acceptable Syrian rebels in 2011 "left a big vacuum, which the jihadists have now filled."
Clinton's dismissal of Obama's foreign policy philosophy was contemptuous. "Great nations need organizing principles, and 'don't do stupid stuff' is not an organizing principle."
Circumstances have changed, so the once-loyal secretary of state, now contemplating her second presidential candidacy, was engaging in Clintonian triangulation. She would be less rough than Bush, less dreamy than Obama: a Goldilocks candidate.
But perhaps circumstances have not changed so much. After Obama adviser David Axelrod tweeted that "stupid stuff" referred to the Iraq war, Clinton announced she was ready to hug the president again. There are lots of left-wing peacenik voters in Democratic primaries. You have to win the nomination before getting to the general election.
Clinton's turnaround was not as surprising, however, as Obama's. The president who declared in June 2011 that "the tide of war is receding" and that the long wars in Iraq and Afghanistan "will come to a responsible end" has ordered hundreds of U.S. troops back to Iraq and launched air strikes with no end in sight there.
For a politician whose range of acceptable positions has previously been very narrow, this is an astonishing turnaround. There is only one explanation: Obama's foreign policy is in shambles.
Decisions he took in 2011, perhaps with the 2012 election in mind, have come to seem gravely mistaken. The refusal to aid Syrian rebels, which Clinton opposed in internal administration councils, has left the field open to the Islamic State rebels who control much of Syria and Northern Iraq and threaten U.S.-friendly Iraqi Kurdistan.
The decision to leave Iraq without a residual U.S. troop presence, contrary to military leaders' recommendation to station 10,000 there, has left the U.S. with little political or military leverage.
Obama now cites Iraq's refusal to give parliamentary approval of a status of forces agreement as the reason for total withdrawal. But he did have administrative approval, which is the basis for American status-of-forces agreements elsewhere.
In the 2012 foreign policy debate with Mitt Romney, Obama sang a different tune. He didn't want a SOF agreement, Obama said: "What I would not have done is left 10,000 troops in Iraq that would tie us down."
That stand was within the narrow range of positions Obama found acceptable. Keeping troops in Iraq was not.
Now, it cannot be said for certain that different decisions would have produced optimal results. Aiding Syrian rebels was a dicey proposition at best, and there was no guarantee it would have produced an acceptable alternative to the Assad regime.
Keeping a troop presence in Iraq might not have prevented the dysfunctional course of the al-Maliki government, either. But it probably would have imposed some restraint. And it would give the United States a better logistical position to repel the Islamic State, protect the Yazidis and guard Kurdistan than we have now -- the goals Obama says he is now pursuing.
No president can anticipate all the twists and turns the world will take during his tenure in office. But this president has been proven dreadfully wrong. Between rounds of golf and political fundraisers -- first things first -- he has been forced to realize that America cannot withdraw from troublesome parts of the world without terrible consequences.
(Daily Corinthian columnist Michael Barone is senior political analyst at the Washington Examiner, a resident fellow at the American Enterprise Institute, a Fox News Channel contributor and a co-author of The Almanac of American Politics.)