By Swanee Hunt

(CNN) -- Sen. Kamala Harris' Martin Luther King Jr. Day announcement that she is running for president puts the number of women who are competing or have declared exploratory committees at four. In defiance of the norm, most of the high-profile candidates bear little resemblance to the 45 presidents in US history.

Harris, in particular, gives us a glimpse at a new reality -- a leader who embodies the convergence of race and gender in America. Consequently, this moment is more than a milestone -- it's a ground-gripping convulsion.

Race and gender causes have long had a love-hate relationship. The struggle between male abolitionists and women's suffrage campaigners came into focus 150 years ago. Despite their sacrifices as they supported the vote for black men, women were shunned by male leaders of the abolition movement

Escaped slave and human rights advocate Frederick Douglass, the MLK of his time, insisted on restraint when women demanded the vote -- not only for black men but also for themselves and their sisters. It would be political folly, Douglass reasoned, to ask the (white and male) electorate to see their power diluted by women as well as black men.

But in this battle over suffrage, Douglass was up against Elizabeth Cady Stanton, best friend and scribe for Susan B. Anthony, who threw out one feminist argument after another. Years later Douglass described that repartee: "I could not meet her arguments except with the shallow plea of 'custom,' 'natural division of duties,' 'indelicacy of woman's taking part in politics. ...' "

Despite Stanton's tight logic, she lost that ideological battle. It was 50 years between a constitutional amendment guaranteeing black men a place at the polls and one establishing women's right to vote.

Further, to appease Southerners, white women carried the torch for suffrage since they were more socially acceptable standard bearers. As an example, when a historic women's march was organized in 1913, race was a source of deep friction between the white and black leaders. Courageous heroes such as lynching chronicler Ida B. Wells were at first told they could not participate. On the day of the march, after a deluge of angry telegrams, the organizers relented and said they could join -- but at the back of the parade.

Harris promises a future in which race and gender are no longer adversaries. And the best part is: She, as well as her female opponents, actually have a shot.

Here's why: Since Hillary Clinton's loss, women have become significantly more politically active. They are running -- and winning. As we watched 2018 breaking news returns, a subplot was rolling across the bottom of our screens. Women were winning seats as governors, state legislators, mayors, school board presidents and more. It was clear to me that they, and women accomplished in other fields, would fill the pipeline to Congress. But only recently have I realized that that same surge will push already elected women further up the ballot and, eventually, into the Oval Office.

The timing of Harris' announcement is also significant, coming toward the end of a three-day holiday devoted to women's rights and civil rights. On Saturday morning, protesters gathered across the country for the third annual Women's March, which first began the day following Trump's inauguration in 2017.

I was struck by two differences compared to the march two years ago. First, although crowds were smaller, there were much wider shoulders to bear responsibility for saving our democracy. A substantially larger number of men, from young fathers to grandfathers, were in the streets. Their signs were easy to spot, high above the heads of other marchers. My favorite was "I'm here for her," the words surrounded by arrows pointing in different directions across the crowd.

Less heartwarming was the second difference. In public descriptions, the march was repeatedly framed as imploding under the weight of division among the leaders. However painful, ruptures are part of any expanding social movement and represent hard-won growth. In a maturing crusade, irreconcilable differences in histories, current realities and visions find expression as the motivating euphoria wanes.

How fitting that the march occurred on Martin Luther King Jr. weekend. That civil rights giant must have spent untold hours protecting his back not only from white supremacists but also other black activists who had moved away from him and now found him too strident or meek, too calculating or naïve.

If we're disturbed by anger among organizers of the march, it's because we've assumed women are so committed to a common goal that they'll inevitably walk arm in arm protesting sexism and its evil cousin, misogyny. We're disillusioned that women are in conflict, because we assume they'll always collaborate.

The same assumption that women will work together (and disappointment if they don't) can be true in the next presidential race. It's inconceivable that we'll ever again see a Democratic debate with a chorus line of men plus Hillary Clinton. And even as there were dozens of woman-to-woman races in the congressional midterms, as the presidential primary field narrows, Harris may well face at least one of her sisters in the Senate. There, 25 female senators are bonded by intimate dinners and mutual friendship. Perhaps Republicans at the table will hold the bandages ready for their Democratic colleagues.

On Saturday night, I sat at a Washington dining table with some of the district's smartest political thinkers. A longtime journalist asked each of us to name the Democratic contender who should top the ticket. The conversation that ensued was as little about white men as the Democratic race looks right now -- and this is truly promising.

It's been more than five decades since King invoked, "We shall overcome because the arc of the moral universe is long, but it bends toward justice." We can't predict 2020. But we can say with certainty that with Harris' announcement, his storied arc has bent a bit more.