MICHAEL BARONE: Obama forced by events to reverse course — and disillusion base.

One of his chief advantages over Hillary Clinton in 2008 was her vote for the Iraq war resolution in 2002 and Obama’s opposition to it, albeit as a state senator from an overwhelmingly Democratic district.

In the late 1960s Democrats switched from being the more hawkish of our two parties, more likely to support military interventions and commitments, to being the more dovish. Visceral opposition to military action, and suspicion that even the most limited such action will lead to massive war, is deeply implanted in many Democratic voters.

You can expect, therefore, a skittish reaction to Obama’s announcement of a military escalation from senatorial and congressional candidates in states with dovish Democratic electorates like Colorado and Iowa. We also may also see depressed turnout of Democratic doves all over the country in November.

It is apparent that Obama’s decision to take military action against the Islamic State of Iraq and Syria, however limited, came despite his deep-seated feelings and was forced on him by events. American voters do not take kindly to videotaped beheadings of Americans. It unleashes a Jacksonian impulse to wipe the people who do these things off the face of the earth.

Obama, like his predecessor, likes to depict Islam as a religion of peace. An unhappily large number of Muslims, however, have other ideas. Their aggression and immunity to appeasement have forced the president to take actions that he, like many of his fellow Democrats, abhors.

Yeah, that keeps happening.