(CNN) — Washington (CNN) -- The nation's growing acceptance of same-sex marriage has happened in slow and painstaking moves, eventually building into a momentum that is sweeping even the most unlikely of converts.
Even though he said in 2008 that he could only support civil unions for same-sex couples, President Barack Obama nonetheless enjoyed strong support among the gay community. He disappointed many with his conspicuously subdued first-term response to the same-sex marriage debate.
Last year, after Vice President Joe Biden announced his support, the president then said his position had evolved and he, too, supported same-sex marriage.
So it was no small matter when on Thursday the Obama administration formally expressed its support of same-sex marriage in a court brief weighing in on California's Proposition 8, which bans same-sex weddings. The administration's effort was matched by at least 100 high-profile Republicans — some of whom in elections past depended on gay marriage as a wedge issue guaranteed to rally the base — who signed onto a brief supporting gay couples to legally wed.
Then there are the polls that show that an increasing number of Americans now support same-sex marriage. These polls show that nearly half of the nation's Catholics and white, mainstream Protestants and more than half of the nation's women, liberals and political moderates all support same-sex marriage.
According to Pew Research Center polling, 48% of Americans support same-sex marriage with 43% opposed. Back in 2001, 57% opposed same-sex marriage while 35% supported it.
In last year's presidential election, same-sex marriage scarcely raised a ripple. That sea change is not lost on the president.
"The same evolution I've gone through is the same evolution the country as a whole has gone through," Obama told reporters on Friday.
Craig Rimmerman, professor of public policy and political science at Hobart and William Smith colleges says there is history at work here and the administration is wise to get on the right side.
"There is no doubt that President Obama's shifting position on Proposition 8 and same-sex marriage more broadly is due to his desire to situate himself on the right side of history with respect to the fight over same-sex marriage," said Rimmerman, author of "From Identity to Politics: The Lesbian and Gay Movements in the United States."
"I also think that broader changes in public opinion showing greater support for same-sex marriage, especially among young people, but in the country at large as well, has created a cultural context for Obama to alter his views."
For years, Obama had frustrated many in the gay community by not offering full-throated support of same-sex marriage. However, the president's revelation last year that conversations with his daughters and friends led him to change his mind gave many in that community hope.