Most presidential candidates would have brushed aside the young woman's challenge, perhaps mumbling something polite about agreeing to disagree.
Not Rick Santorum, on that January afternoon in a hotel ballroom full of college students in Concord, N.H. He was going to convince her (and the entire room) that, no, the inherent right to happiness does not mean society should permit two gay men to marry.
"So if you're not happy unless you're married to five other people, is that OK?" Santorum said, as boos washed over him. "Well, what about three men?"
In a few moments, he had gone from a triumphant candidate surging in the polls after Iowa to a pilot on the verge of a corkscrew dive. It caused onlookers to hold their breaths but was entirely in character for the former Pennsylvania senator and noted social conservative. He can't help being true to himself.
On Tuesday, Santorum brought to a close a presidential campaign that had exceeded everybody's expectations, including his own. In the end, the authenticity on display that January day helped carry him to dizzying heights in the GOP race - and may have also helped bring him down.
Starting as an asterisk in the polls, he rose up to win more than three million votes and carried 11 caucuses or primaries. He was the last conservative challenger standing in Mitt Romney's way.
"We won more counties than all the other people in this race combined," Santorum noted in a Gettysburg speech announcing the suspension of his campaign.
True; he carried 902 counties. But Romney won more people, sweeping the populous suburbs filled with the more moderate-minded swing voters the GOP needs.
At a crucial point before February's Michigan primary, when he could have grievously wounded Romney by beating the front-runner in his native state, Santorum let himself stray from his message of economic populism - symbolized by his moving evocations of his coal miner grandfather - into controversial comments on social issues.
It was reminiscent of 2006, when Santorum lost his Senate reelection bid in Pennsylvania by 17 percentage points, passionately talking of morality and the family and warning of the dangers of Islamic terrorism and Iran.
"Rick allowed himself to be drawn slightly off message in that 2006 campaign, and we saw some of that in this campaign," said a friend, conservative activist Colin A. Hanna of Chester County.
"The reason for that is his intellectual integrity," Hanna said. "If a question is raised that the typical professional politician would duck or dodge, Rick addresses it. That makes him vulnerable to traps."
Running on shoe leather. Santorum made his first visit to Iowa in 2009, at the invitation of a conservative group holding a conference in Dubuque. As the campaign heated up in 2011, he toiled in obscurity, regularly finding himself at the farthest reaches of the stage when the crowd of GOP candidates met for their near-weekly debates.
As late as December, Santorum was traveling from town to town in Iowa with a couple of aides and one or two of his children, visiting the ubiquitous Pizza Ranch restaurants and libraries and cafés. A supporter, Chuck Laudner (whom Santorum thanked Tuesday in his speech), ferried him from stop to stop in a silver Dodge Ram pickup.
They hit all 99 counties in Iowa, an old-school, shoe-leather approach, and he became the momentum candidate. As other conservative alternatives such as Texas Gov. Rick Perry fell by the wayside, Santorum gained.
He was riding high after victories in Colorado, Minnesota, and Missouri on Feb. 7. Polls showed Michigan within his grasp, and kept alive conservatives' doubts about Romney.
Then Santorum was pulled back into extended conversation about contraception and other social issues.
He defended earlier remarks that he "almost threw up" on reading John F. Kennedy's famed 1960 speech about separation of church and state. He defended his belief that birth control is sinful (while taking care to say he did not want to outlaw it). At a suburban Detroit forum, he called President Obama a "snob" because "he wants everyone to go to college."
Romney, on the strength of a barrage of attack television ads and mailers, came from behind to win Michigan. Santorum took Mississippi, Alabama, and Louisiana, but lost Ohio, Illinois, and Wisconsin - big, industrial swing states with more varied electorates.
The fact that Romney was in his second run for the GOP nomination showed in his advantages of organization - and cash. "When you have millions and millions of bucks, it's much easier to pound through," said David Urban, a Washington lobbyist and informal Santorum adviser.
The exit polls were stark. Santorum was able to consolidate the support of evangelical Christian voters and those who described themselves as "very conservative." Indeed, Romney did not win any state where evangelicals were at least half the vote.
And those voters' energies, too, are crucial to the party's fortunes in the fall.
"Rick Santorum was a reliable force to carry the voice of social conservative and values voters in this race," said Bruce Haynes, a Washington-based GOP strategist. "These are voters that the Republican Party needs to have engaged, to feel that their voices have been heard, in order to win. . . . No cultural conservative in the party can say they didn't have their shot. In that sense he performed an important function."
At the same time, Santorum and the battle he waged for the soul of the party may help explain some of the polling difficulties that Romney now faces with independent voters and women, said Villanova University political scientist Lara Brown.
"In dropping out, Rick Santorum certainly helped his own fortunes, but I don't know if he's going to help the Republican Party's fortunes," she said. "There is probably a case to be made that he has spooked independents and moderates."
Gerald Shuster, who teaches political communication at the University of Pittsburgh, noted that by dropping out, Santorum avoided the possible humiliation of losing his home state's April 24 primary.
"Do you think, if he had a realistic chance of beating Mitt Romney in Pennsylvania - given his personality and his arrogance - that he would have gotten out prematurely?" Shuster said. He also suggested Santorum's stridency on social issues may limit his future role.
Haynes, however, said Santorum can have influence if he plays his hand right.
"Is he going to be a rallying force to help bring the varying parts of the Republican coalition together and work to defeat the president? Or is he going to take a powder and keep his distance from Romney?" Haynes said. "To use his own phrase, it's time to be a team player again."
Contact Thomas Fitzgerald
Staff writer Tom Infield contributed to this article.