North Carolina Republican Senator Richard Burr cited a "generational change" in American attitudes toward homosexuality for his surprising change of heart to allow gays to serve openly in the military.
Indeed, an overwhelming shift in public opinion served as the catalyst for the Senate's move to repeal the "don't ask, don't tell" policy - a lightning rod of America's culture wars that had seen thousands of military personnel discharged for exposing, purposely or not, their sexuality since the controversial rule was adopted by Bill Clinton in 1993.
But for President Barack Obama, who had campaigned on repeal, pure luck played just as big a part in ending a discriminatory policy that has left the American military an outlier among the developed world's armies.
The Senate's 65-to-31 vote on Saturday was only made possible when an exceptionally narrow window of opportunity opened once Congress passed Mr. Obama's $858-billion (U.S.) package of tax cuts on Thursday. That window was closing rapidly as lawmakers prepared to leave for the holidays, only to be replaced by a more conservative Congress in January.
It was now, or perhaps not for a long time to come. The new Congress will be dominated by a resurgent Republican majority in the House of Representatives and a more right-wing GOP bloc in the Senate.
That reality left Senate majority leader Harry Reid with less than 48 hours after the tax bill's passage to twist arms and make deals. But for the agents of logrolling in the U.S. Congress, winning on one issue almost always entails losing on others.
By corralling sufficient votes to repeal the military ban on gays, Mr. Reid sacrificed a bill that he had personally championed to provide a path to citizenship for minors brought to the United States illegally by their parents. And by forcing a vote on the military ban, he may have irritated enough right-wing Republicans to torpedo chances that the Senate will ratify Mr. Obama's signature nuclear-arms treaty with Russia.
For the President, the ending of "don't ask, don't tell" is a second major legislative win in less than a week, after he overcame revolt in his own party to win passage of a deal to extend Bush-era tax cuts for the wealthy and implement a series of tax breaks to kick-start the economy.
But the Senate's rejection of the so-called DREAM Act - aimed to provide permanent residency status to illegal immigrants who attend college or join the military - made the other victories bittersweet. On Saturday, the bill, which the President had lobbied hard for as a step toward fulfilling a promise of comprehensive immigration reform, fell five votes short of the 60-vote threshold needed to advance in the Senate.
"The fight for civil rights, a struggle that continues, will no longer include this one," Mr. Obama said of the military ban in an e-mail sent to members of Organizing for America, his Internet-based campaign unit. "But the rightness of our cause does not guarantee success, and celebration of this historic step forward is tempered by the defeat of another."
Hundreds of Hispanic youths watched from the Senate gallery as the DREAM bill went down to defeat, many of them erupting into tears. For them and thousands of others who had attended rallies across the country in recent weeks, this legislative loss constitutes their formative political experience.
"This is a vote that will not soon be forgotten by a community that is growing not just in size, but in power and political awareness," insisted New Jersey Democrat Robert Menendez, the Senate's only Latino member.
For another minority group, however, confidence in the political process emerges vastly enhanced by the Senate's unexpected move to repeal the military ban on homosexuals. Indeed, even though Pentagon leaders themselves favoured repeal, advocates for gay rights had increasingly believed their only hope for ending the ban lay with the courts.
In October, a district court judge in California struck down "don't ask, don't tell" and the case was ultimately expected to land before the Supreme Court. But proponents of repeal may be lucky Congress acted first.
"'Don't ask, don't tell' was quite possibly one of the worst cases for gay-rights advocates to bring to the courts," University of Colorado law professor Scott Moss said in an interview. "The Supreme Court has not declared that sexual orientation is as protected as race or gender. It has refused to go that far."
Even so, Prof. Moss conceded that Congress's repeal of the military ban on gays could buttress the legal case for gay marriage. A federal court judge struck down California's prohibition on same-sex marriage in August and the case is expected to end up before the Supreme Court by 2012.
"Every barrier based on sexual orientation that is broken down does create momentum for gay marriage," Prof. Moss offered.
Still, the current Supreme Court may not see it that way. And neither, for that matter, does this President.
But as with all struggles for equality, the operative word may be "yet."