It was not until 2012 that Obama announced his own support for gay marriage. Now, he says, the court ruling will end the patchwork of laws on marriage across the country and the uncertainty that they create for same-sex couples.
Immediately after the ruling, Obama tweeted: "Today is a big step in our march toward equality. Gay and lesbian couples now have the right to marry, just like anyone else. #LoveWins"
And there's division among several of the Republican candidates for president about the Supreme Court's decision to legalize same-sex marriage nationwide.
Former Pennsylvania Sen. Rick Santorum has condemned the decision by what he calls "five unelected justices" who make up the ruling's 5-4 majority.
Santorum is a social conservative, and he says the court has redefined "the foundational unit that binds together our society, without public debate or input."
Former Arkansas Gov. Mike Huckabee tweets that the ruling is "irrational" and "threaten religious liberty" and Congress must act.
Another Republican hopeful, former technology executive Carly Fiorina, also takes issue with the court redefining marriage, as she sees it. But she doesn't dispute the conclusion. She says she's always believed "all Americans should have equal benefits and rights."
Another rival, South Carolina Sen. Lindsey Graham, says he'll "respect the court's decision."
He calls himself "a proud defender of traditional marriage." But the senator says it's futile to attempt a constitutional amendment limiting marriage to a man and a woman.
Democratic presidential candidate Hillary Rodham Clinton was clearly prepared for the Supreme Court's ruling to legalize same-sex marriage in all 50 states.
Clinton fired off several tweets after the court issued its 5-4 decision, and her Facebook and Twitter profile pictures are now a rainbow version of her "H'' campaign logo.
She says in one tweet, "Proud."
Another message shows a graphic of the country with all states colored in gold, showing marriage equality is now the law. She adds, "Our new favorite map."
In yet another Twitter message, she says "Proud to celebrate a historic victory for marriage equality — & the courage & determination of LGBT Americans who made it possible."
Republican presidential contender Jeb Bush is affirming what he calls a faith-guided belief in traditional marriage in the wake of the Supreme Court's ruling legalizing gay marriage nationwide. He's also echoing his familiar theme that states should make such decisions.
But the former Florida governor breaks with some of his party's social conservatives by saying: "I also believe we should love our neighbor and respect others including those making lifetime commitments."
He adds, "In a country as diverse as ours, good people who have opposing views should be able to live side by side."
Bush is a converted Roman Catholic and he typically says he supports traditional marriage. But he notably does not condemn same-sex marriage in the same way as some of his 2016 rivals.
In New Hampshire last month, he told voters there are indeed some single-issue voters but not as many as people believe.