Obama has reestablished productive diplomacy as the central task of a progressive foreign policy, and as a viable alternative approach to dealing with countries the GOP foreign policy establishment would rather bomb. He established a viable alternative to the liberal hawks that dominated Democratic thinking during the Bush years, and held positions of influence on Hillary Clinton's 2008 campaign.

Obama, by contrast, achieved two huge openings to countries the US had previously counted as enemies for decades. They are achievements more like Nixon's opening to China than, say, the SALT accords. And, of course, Obama has a major Russian arms control deal under his belt in the form of New START, as well.

Brian Steensland, a sociologist who studies American social policy at Indiana University in Indianapolis, agrees. "The main thing it does, I think, is establish the expectation in the public’s mind that access to basic health care is a right," he says. "It’s going to be hard to go back to a time when access to health insurance, and the subsidies to help pay for it, wasn’t near-universal."

To pay for it all, the Affordable Care Act cut back on Medicare spending and hiked taxes on rich people's investment income and health plans. It effected a massive downward redistribution of income. It's one of the most startlingly progressive laws this country has ever enacted.

He used executive action to enact bold regulations to curb greenhouse gas emissions, and to protect nearly 6 million undocumented immigrants from deportation. He ended the ban on gay and lesbian service in the military, made it easier for women and minorities to fight wage discrimination, cut out wasteful private sector involvement in student loans, and hiked the top income tax rate. He reprofessionalized the Department of Justice and refashioned the National Labor Relations Board and the Wage and Hour Division of the Labor Department into highly effective forces for workers' rights.

His presidency holds massive symbolic value as proof that the reign of white men over American government can be halted and America as a whole can be represented. And while he was too slow in announcing support for same-sex marriage, he appointed two of the justices behind the Supreme Court's historic decision legalizing it nationwide, and enlisted his Justice Department on the side of the plaintiffs.