At the time, almost everyone supported the Afghanistan invasion — as close to a unanimous national decision as we’ve seen since Pearl Harbor. At the time, based on judgments by the intelligence community about Saddam Hussein’s weapons of mass destruction, a solid, bipartisan majority favored intervention in Iraq — a majority broad enough to include then-Sen. Hillary Clinton. Yet just about no one would have supported the Iraq war if it had been known that Saddam had suspended his WMD programs. It was the prospect of proliferation that elevated Iraq above a containable regional threat.

So the proper answer for Republican candidates (no matter who their siblings might be) when asked if they would have invaded Iraq while lacking the main strategic justification to invade Iraq: Of course not.

But this historical hypothetical says almost nothing about the foreign policy views of a candidate. A better question: What are the lessons a president should draw from American interventions in Afghanistan and Iraq?