Weeks, it is known, are lifetimes in politics, but few packed as much life of all the wrong kind as these last weeks for Democrats, who saw Hillary Clinton break with President Obama on many key Middle East issues, and then saw Obama say that the plan to remove troops from Iraq (before this his proudly held signature issue) had not been his decision itself.

George W. Bush made him do it, or Iraq made him do it, or Bush and Iraq locked him into their policy. It was his admission his policy has been a failure, and at that moment, an era in politics closed.

The issue is not what Bush did in Iraq, but what Obama has done to make the Islamic State possible, and this will define the next age. In 2006 and 2008, Democrats ran against the Bush foreign policy and did very well. In 2012, they ran on their foreign policy and did well enough, as it seemed at the moment to hold things together.

But unless things change fast, in 2014 and 2016, Republicans will run against them on their foreign policy, which has become a disaster: "Lead from behind" has been proved a nonstarter, foreign policy has come back as a very big issue and the Democrats, who a few weeks ago had been marching in lockstep, may be starting their own civil war.

Diehards still blame the Iraqi invasion — the original sin that unhinged the whole region — but two things appear wrong with this theme. Bush broke Iraq in 2003-2006, but put it together in 2007-2008, a feat Obama and Vice President Joe Biden would call in 2011 a substantial accomplishment. Liberals will have to explain how the worst mistake ever became an accomplishment and then a fiasco again while under their leadership.

Point No. 2 is Iraq didn’t collapse on its own but was overrun by militants coming from Syria, a country Bush never invaded and whose civil war he did nothing to cause.

What caused it? The policies pushed by Obama and liberals. "The conclusion that has become conventional wisdom outside the White House is that his retreat in Iraq and passivity in Syria did much to create the ugly monster the United States now faces," Jackson Diehl wrote Friday. "The war is less the result of Iraqi political dysfunction than the civil war in Syria, where the West’s failure to back moderate forces allowed the concentration of militants that birthed the Islamic State."

This is the view of establishment Democrats, who want their side to man up and act more like Harry S. Truman. But obstacles stand in their way.

"Here’s the problem," Jim Geraghty tells us: The Democratic base has become isolationist and doesn’t want "money spent overseas or troops deployed anywhere," and will fight to the end against re-engagement, even by one of their own. "The Democratic officeholders' opportunistic demonization of the Iraq War from 2003 to 2008 has caught up with them. … For the better part of a decade, Democrats insisted U.S. troops could leave Iraq and things would turn out fine for American interests. "

This sets the stage for a brawl in the party, in which the spirit of "Fahrenheit 911" could revive very quickly. The debate over intervention in Syria in 2013 showed both parties splintering, with intervention versus isolationist splits in both parties, bipartisan blocs formed in either direction and the Tea Party split between its Rand Paul and its Marco Rubio sentiments.

The 2016 race has just entered a whole new dimension — and become very interesting, fast.

Noemie Emery, a Washington Examiner columnist, is a contributing editor to The Weekly Standard and author of Great Expectations: The Troubled Lives of Political Families.