Paul Krugman has joined the self-appointed political grownups closing ranks around Hillary Clinton against Bernie Sanders. In a piece titled "How Change Happens," the liberal economist and New York Times columnist insists, "The question Sanders supporters should ask is, When has their theory of change ever worked?"

That must be right. It's an excellent, sober, adult question. The answer, of course, depends what you think the Sanders campaign's theory of change is. Krugman argues, "On the left there is always a contingent of idealistic voters eager to believe that a sufficiently high-minded leader can conjure up the better angels of America's nature and persuade the broad public to support a radical overhaul of our institutions." This, he says, was what drove the Obama campaign in 2008. By implication, he seems to mean other quixotic campaigns, such as George McGovern's in 1972, when McGovern lost forty-nine states to Richard Nixon.

Krugman compares unrealistic, high-minded idealism with "politically pragmatic" governance, like Franklin Roosevelt's during the New Deal. Roosevelt, he reminds us, cut deals with Southern segregationists and introduced programs like Social Security incrementally. Krugman argues that this dirty-hands commitment to halfway measures, not purity, is what it takes to get things done. Versions of this contrast have become a common refrain: Sanders sounds great, but governing, is messy, complicated, grown-up.

Krugman's mistake is very basic. He's wrong about the Sanders campaign's theory of change. It isn't that a high-minded leader can draw out our best selves and translate those into more humane and egalitarian lawmaking. It is that a campaign for a more equal and secure economy and a stronger democracy can build power, in networks of activists and alliances across constituencies. The movement that the campaign helps to create can develop and give voice to a program that the same people will keep working for, in and out of election cycles. In other words, this is a campaign about political ideas and programs that happens to have a person named Bernie at its head, not a campaign that mistakes its candidate for a prophet or a wizard (or the second coming of Abraham Lincoln, who gave us the now-cliché phrase about better angels, but had no delusion that words could substitute for power).



The campaign whose loyalists made this idealistic mistake was, of course, Obama's 2008 run. The candidate spoke so charismatically, and seemed so much to embody a vision of realigned, common-sense, fresh-feeling progressivism, that some of us did imagine he could recast American political loyalties. Back then, Krugman was accusing Obama's supporters of spewing "bitterness" and "venom" and coming "dangerously close to a cult of personality." Now he's pleased that President Obama, unlike Candidate Obama, has governed rather like a Clinton: pragmatically, with the hand he was dealt. He seems to think that supporting Sanders's "purist" positions means "prefer[ing] happy dreams to hard thinking about means and ends." And so, he wants us to think, if we are going to be political grownups, we had better put away childish things. Like talk of truly universal health care (his only example of Sanders's alleged extremism) or, probably, the term "socialism," whose revival is baffling pundits everywhere.

Adulthood is charismatic and daunting. It always seems to have the drop on you. But sometimes it just doesn't understand.

Yes, F.D.R. governed "pragmatically," in the sense that he counted votes and cut deals. Everyone does this, with the occasional exception of Daenyras, Mother of Dragons. But what made it possible for him to pass sweeping changes in economic regulation and social support, changes so radical that his enemies accused of socialism, of being un-American, of destroying the country and becoming an American Mussolini? The answer is in two parts: ideas and power. His administration stood at the confluence of two great movements. The first was the labor unions, which had been building power, often in bloody and terrible struggles, since the late nineteenth century. The second was made up of the Progressives, generations of reformers who worked in state, cities, and universities -- and occasionally in national government - to achieve economic security and update political democracy in an industrial economy that had transformed the country in the decades after the Civil War. Ideas, programs, and power swirled around Roosevelt, gave his agenda shape, and pressed it forward.

These movements were sources of ideas, and also of power. Why did all those enemies and reluctant allies end up meeting Roosevelt halfway? The answer was not not his pragmatic attitude. The reason that even some who hated him had to compromise with Roosevelt or give way was the political force he could marshal. His theory of change was no more about compromise than it was about high-minded words: It was about power. Compromise was a side-effect, a tactic at most.

But the central place of power does not mean idealism had no place in the New Deal. Roosevelt explained what he was doing, and why, in language that was more Sanders than Clinton, more vision than wonkery. He famously called for a Second Bill of Rights, an economic program of security, good work, and material dignity. Going back to the Founders to ground the welfare state is, let's say, idealistic. And, while F.D.R. was willing to compromise, he was also willing to draw hard lines, calling out "economic royalists" and saying of his enemies, "They are unanimous in their hate for me -- and I welcome their hatred."

Wow. You might hear that from Ted Cruz or possibly Donald Trump this year, but not from any of the Democrats. Roosevelt used the highest idealistic language and the toughest words of conflict. They conveyed the vision behind his program and forced other politicians to form battle lines on the landscape he defined. Then, and only then, he compromised, on his terms.

The banal response to Krugman would be that most politicians campaign in poetry and govern in prose -- with the exception of some recent Democrats, notably Hillary, who ease his admirably wonkish heart by never leaving prose mode. Don't fear the poetry! one might say: it is not a theory of change, just a normal way of talking in a democracy.

But the real answer is deeper. Obama ran in poetry and has governed in prose, in quite a literal sense that one could diagram in the sentences of his speeches and press conferences. But in the stronger, older tradition of campaigns based on ideas and programs rather than personalities, candidates run to build power, and use idealistic language to explain why that power matters. Then, if they get to govern, they use it.

That is a theory of change. To answer Krugman's question: yes, it has worked. In fact, it may be the only theory of change that has ever made democracy real. It is politics for adults.