Throughout its history, the National Mall in Washington has been the site of protests and rallies by Americans seeking redress of grievances, yet few have been so consequential as the 1963 March on Washington that provided the occasion for the Rev. Martin Luther King's famous "I have a dream" speech. In that memorable oration, Mr. King summed up African-Americans' struggle for civil rights by calling on the nation to live up to its historic promise of equal justice and opportunity for all.

Saturday, a coalition of progressive activists will gather on the Mall to reaffirm Mr. King's expansive vision of social justice, though in a very different context than the one that framed the 1963 march. Where the earlier event took place during the high tide of the civil rights movement and at a time when the country was of achieving momentous change, today's activists will be meeting at a moment of conservative retrenchment when the mood of the country seems more focused on the past than on the future.


In August, for example, on the anniversary of the 1963 march, conservative TV talk-show host Glenn Beck organized what he billed as a "Restoring Honor" rally on the Mall, featuring former Alaska Gov. Sarah Palin. Not surprisingly, Ms. Palin, darling of the right-leaning tea party movement, told her audience that government was the real problem for what ails America today and that any authentic grass-roots movement had to rein in a federal bureaucracy that had grown much too large and was spending way too much.

But then she and Mr. Beck went further by making the surprising suggestion that the tea partiers' call for smaller, more limited government actually made them, rather than the old civil rights coalition, the true spiritual heirs of Mr. King's empowering message. They were wildly applauded by those in attendance.

That surely galled progressives across the country, who view the tea party's fat-cat corporate sponsors and virtually all-white membership as a reactionary movement aimed at undoing the hard-won gains Mr. King and his followers struggled so hard to achieve. From their standpoint, the tea party's claim to the King legacy in order to stir up anti-government hysteria showed a cynical disregard for the fact that it was Mr. King's call for federal intervention, after the refusal of popularly elected state and local governments to act, that finally led Congress to enact the landmark civil rights legislation that ended segregation and restored the right to vote to millions of black Americans in the South.

So Saturday's gathering of a broad spectrum of progressives on the National Mall under the banner of "One Nation, Working Together," is first of all a riposte to the tea party's attempted appropriation of Mr. King's moral authority, as well as its claim to speak for a broad swath of the American middle-class that has been hit hard by the recession.

Progressive criticism of that latter point is especially pointed in light of earlier news reports suggesting that tea partiers, as a group, are significantly better off financially that most Americans and have not suffered nearly as much from the loss of income and employment plaguing the rest of the country. The fact that tea party organizations are also getting a good deal of their money from just a few wealthy individuals with long-standing ties to ultra-conservative organizations and causes makes the movement's populist pretensions to speak for ordinary Americans doubly suspect.

The rally is also an attempt to rekindle some of the enthusiasm millions of people felt during the 2008 election campaign that saw Barack Obama become the nation's first African-American president. A lot of that energy has cooled since then in the face of stubbornly high unemployment and a Congress so paralyzed by partisan rancor that many people have lost faith in the government's ability to do anything to help improve the lives of ordinary Americans.

The "One Nation" rally's organizers hope to bring thousands of supporters to the nation's capital in a collective show of force that matches the August tea party rally in both numbers and enthusiasm before November's mid-term elections.

Benjamin Jealous, the dynamic young president of the National Association for the Advancement of Colored People, is one of the lead organizers of today's event, and he has struggled mightily to reach out to other groups that share the ideals Mr. King stood for. A half-century after Mr. King's defining moment on the steps of the Lincoln Memorial, it's worth remembering that the civil rights movement he championed became the template for all the great social transformations in American society that followed, from the women's movement and new protections for Native Americans, Latinos and the disabled, to today's struggle for equal rights for gays and lesbians in the military and the right of gay people to marry.

The tea party's backward-looking agenda, with its narrow-minded interpretation of the Constitution, its emphasis on America as a Judeo-Christian country and its celebration of the founding fathers' "original intent," despite their willingness to create a nation that both tolerated slavery and relegated women to second-class citizenship, is at bottom an attempt to deny the multi-ethnic, multicultural diversity, tolerance and adaptability to change that made America great.

There's no turning back the clock to look for solutions in some idyllic vision of an 18th-century rural society, which mostly never existed anyway except in the minds of people who fear to face the challenges of 21st-century postindustrial America. What the tea party seems not to understand is that conservatism, too, must adapt to changing times. By contrast, the progressives gathered on the Mall in Washington today recognize that change is a constant, and that the truest measure of love of country is a willingness to work together toward making an ever more expansive ideal of social justice into reality.