President Obama's statement supporting same-sex marriage yesterday was a cautious "outing" of his shift on a divisive social issue that made him balk in the past.

It's a classic case of moving a leader toward a historical moment by moral suasion. Quaker abolitionists pressed and lighted the way toward slave emancipation for Civil War President Lincoln. It's heartening to see the technique working 150 years later.

Vice President Joseph R. Biden Jr. was among many advisors who leaned on the president to find a new place on the map. Signs of social "mainstreaming" came from the mayors of San Francisco and New York, fundraisers on both coasts and even Obama's own family. The New York Times began covering gay celebrations. Legal scholars affirmed the constitutionality of gay marriage. And most know a gay couple who took vows — or wish they could.

Yet Obama, running hard for re-election, is a true believer in the vanishing middle ground. Come the fall, he may lose North Carolina (which voted to ban gay marriages Tuesday). He won that swing state in 2008. Backing gay civil unions then was the perfect political pass on thorny terrain. Was he wistful to surrender that patch?

Perhaps that's why Obama's sotto voce remarks seemed lukewarm. He spoke "for me personally" in an interview, not in a speech. The contrast to Biden's emphatic words endorsing marriage equality on a Sunday talk show was clear. Whether Biden meant to make the water warmer or whether his outburst forced the president's hand is Washington's guessing game.

Either way, Obama had to speak out. It wouldn't do for his Democratic Party base, a Cabinet secretary, a handful of governors and senators — and runaway Joe Biden — to leave him at the station.

Gays serving openly in the military is a landmark of progress Obama was proud to sign. But the new frontier of gay marriage, spreading as fast as homesteading once did out on the plains and prairies, made him squeamish.

Obama's move shows the force of moral suasion to get things done. There's no better way to make social change. It takes years, but produces a consensus that something's got to give: apartheid, colonialism or Jim Crow laws. Related to nonviolent resistance, it works on an individual conscience.

Moral suasion is applied to a leader by influential change-makers, often out of sight. In 1862, shortly before Lincoln freed the slaves, a delegation from Society of Friends (aka Quakers) visited Lincoln to urge emancipation, which the society had championed first. While Quakers prayed silently with the president, the woman there spoke as the spirit moved her. Lincoln wept. He knew it was written in his words on the wind of change. No abolitionist at first, he "evolved" in less than 18 months.

As welcome as it is, this is no Lyndon Baines Johnson moment, a law won by the sweat of the presidential brow. Obama's change of heart can't compare to the monumental Civil Rights Act. Robert Caro's new biography volume, "The Passage to Power," shows how he plied his political skills for the greater good of fairness. Many Southern whites felt they had a lot to lose if Jim Crow laws were lifted from the land. Johnson took them head-on. Obama does not spend his days that way, in the thick of things.

Yesterday was a long time coming for human rights advocates. Seen in the hard light of strategy, Obama cheered his half of an unhappy country, and it didn't cost a dime. Compared to Lincoln and Johnson's mountains, marriage equality is an easy winner, a hill to climb. In the end, the American journey to social justice must never end.

To find out more about Jamie Stiehm, and read features by other Creators Syndicate writers and cartoonists, visit www.creators.com.