The Supreme Court handed down major victories for gay marriage. The Post’s Robert Barnes breaks down the DOMA and Proposition 8 decisions from the courthouse steps. (The Fold/The Washington Post)

The Supreme Court met the moment Wednesday. With public attitudes shifting dramatically in favor of same-sex marriage, the justices used a pair of rulings to give additional momentum to one of the most rapid changes in social policy in the nation’s history.

Sometimes the court makes history outright, as it did when it outlawed segregated schools in 1954 or legalized abortion in 1973. Other times, it moves more deliberately, facilitating changes already underway. That was the case on Wednesday. The justices carefully provided a historic push to the same-sex-marriage movement, even as they decided to leave the political wrangling over the issue to the states and politicians.

Everything about the decisions on the Defense of Marriage Act (DOMA) and California’s Proposition 8 suggests that the justices fully recognize the direction the national debate is heading in and were not prepared to stand in the way. The throngs outside the Supreme Court were dominated by supporters of same-sex marriage, and their jubilation showed that they regarded Wednesday as a momentous day in the movement for marriage equality.

By every measure, more and more Americans are coming to accept the idea that such unions should be legal, part of a cultural change of enormous significance.

But the shift in public opinion is neither fully realized nor held consistently nationwide, or among all demographic groups. Same-sex marriage continues to divide Americans on the basis of ideology, political party, age and region, which is why legal and political battles will continue after Wednesday’s rulings. The justices seemed aware of that as well.

The court said it will provide federal recognition (and therefore benefits) to the legalization that has taken place in a growing number of states but not require the states that still bar such unions to overturn those laws. Yet in doing what it did, even in stopping short of declaring same-sex marriage a constitutional right, the court provided strong assistance to proponents for the battles ahead.

In one sense, the politics of same-sex marriage already had reached a tipping point. Less than a decade ago, Republicans considered the issue a valuable political weapon with which to rally conservatives and put Democrats on the defensive. Today, although a majority of Republicans continue to oppose same-sex marriage, Republican leaders and candidates are on the defensive. Their positions may not have changed but many of them are silent on the issue, particularly in the context of political campaigns.

Thirty years ago, the culture wars split the Democratic coalition and left the party on the defensive in national elections. Whether it was abortion, affirmative action, drugs, gay rights or the broader debate over traditional values, Democrats were divided, Republicans united.

Today it is the opposite. President Obama and the Democrats use the issue of same-sex marriage — or gun control or climate change — to try to broaden and deepen their coalition, particularly among younger voters. This coalition, along with the votes of African Americans and Latinos, propelled Obama to reelection in November and it keeps growing larger as the nation’s demographics continue to change.

Recent votes in states such as Maryland and Minnesota have underscored the momentum that proponents of same-sex marriage have. The court’s ruling on Proposition 8 will once again add California, the nation’s most populous state, to the list of jurisdictions where such unions are legal.

But in other ways, the battle continues to rage. Same-sex marriage is not legal in more than three dozen states. Many of those states have written the bans into their constitutions. It could take years to change those provisions if the battles are engaged one by one, state by state. Only the Supreme Court could short-circuit that process.

For now, the justices are not willing to do so. That is not to say that, in a few years, as additional tests are brought before these justices or a court with a different composition, there will be no change. But as some proponents of same-sex marriage noted Wednesday, the struggle of rights rarely happens in a single judicial thunderclap.

Obama, en route to Africa, hailed the court’s ruling on DOMA in a tweet.

Republican leaders voiced their disappointment with varying volume and vowed to keep fighting to preserve traditional marriage.

Congressional Republicans had risen to defend DOMA before the court when the Obama administration said it would no longer do so, and House Speaker John A. Boehner (R-Ohio) voiced his disappointment with the court’s decision.

“A robust national debate over marriage will continue in the public square,” he said, “and it is my hope that states will define marriage as the union between one man and one woman.”

Other social conservative leaders decried the ruling in more vehement terms. Former Arkansas governor Mike Huckabee, a 2008 presidential candidate, said, “Jesus wept.” Others denounced the decision as a “stunning and indefensible display of judicial activism,” as Ralph Reed, chairman of the Faith and Freedom Coalition, said in a statement.

The Republicans can look ahead to growing divisions within their ranks over this and other cultural issues. Those tensions are likely to intensify if public opinion continues to move in the direction of support for same-sex marriage and prospects for winning national elections diminish.

Democrats are united on the issue. It is likely that anyone who seeks the party’s 2016 presidential nomination will favor same-sex marriage. Whether anyone in the GOP field will back legalizing such unions remains to be seen. But history is moving against Republicans on this, and a high court led by Chief Justice John Roberts — a court that conservatives have looked to for support — did little Wednesday to offer aid or comfort.

For previous columns by Dan Balz,go to