Obama’s speech in Kansas, which just concluded, was the most direct condemnation of wealth and income inequality, and the most expansive moral defense of the need for government activism to combat it, that Obama has delivered in his career. The speech is best seen as a bid to establish a moral and philosophical framework within which literally all of the political and policy battles of the next year will unfold, including the biggest one of all: The presidential campaign itself.

While Obama did pivot to a more populist posture earlier this fall after the debt ceiling debacle, today’s speech was notable for its more direct emphasis on inequality itself as a moral scourge and as a threat to the country’s future. He cast the question of whether government can and should act to combat inequality as a referendum on American values and our national identity.

The clash of visions Obama tried to set the stage for today — a philosophical and moral argument over government’s proper role in regulating the economy and restoring our future — is seen by Dems as more favorable to them than the GOP’s preferred frame for Campaign 2012, i.e., a referendum on the current state of the economy and on Obama’s efforts to fix it. Hence his constant references to the morality of “fairness.”

“We simply cannot return to this brand of you’re-on-your-own economics if we’re serious about rebuilding the middle class in this country,” Obama said, in what will probably be the most enduring line of the speech. A number of people on Twitter immediately suggested a new shorthand: “YoYo Economics.”

That line is key in another way. Dems believe inequality will be central in 2012 because they think there's been a fundamental shift in how Americans view the economy, one rooted in the plight of the middle class and in the trauma created by the financial crisis. As Chuck Schumer told me recently, Dems think the public’s rising anxiety about inequality is not just about the top one percent doing far better than everyone else. Rather, they’ve concluded it’s directly linked to the public’s perception that unfettered capitalism undermined the security and future of the middle class in a very fundamental, frightening way. Occupy Wall Street reflects broader, deeper concerns that are thoroughly mainstream, and no matter what people tell pollsters about government, they want sustained government action when they understand it’s about restoring the middle class’s security and durability.

Obama’s speech went to great lengths to criticize inequality in this context, and his historical references were also designed to support that theme. He drew a direct line between today’s debate and the debate at the turn of the century between the forces of unregulated capitalism, which caused massive inequality and suffering, and Theodore Roosevelt's insistence on humane government intervention in service of the national good.

“Roosevelt was called a radical, a socialist, even a communist,” Obama said, in a tacit reference to similar attacks on himself. “But today, we are a richer nation and a stronger democracy because of what he fought for in his last campaign: an eight hour work day and a minimum wage for women; insurance for the unemployed, the elderly, and those with disabilities; political reform and a progressive income tax.” Strikingly, the validity of some of these same government functions is still being debated today.

Political scientists will tell you that individual speeches don’t matter; and that grand themes are very unlikely to supplant the direct experience of the economy as a motivator of voters. But we’ll be hearing these themes countless times between now and election day. And those who had hoped that Obama and Dems would make an unapologetically populist and moral case against inequality and economic injustice central to Campaign 2012 should be pretty pleased with what they heard today.