To most passers-by, the tens of thousands of people who jammed the sidewalks of Greenwich Village on Sunday were just the typical tank-top-clad revelers of a gay pride weekend.

But to Aaron Levine, a 19-year-old, clipboard-toting volunteer sent there by the Obama campaign, everyone was a potential get. A group of twenty-somethings huddled in the shade under a Starbucks awning trying to stay cool: “They’re perfect,” he said. The long line outside the Duplex, a nightclub with views of the parade route: “They have nothing else to do now but sign up. It’s great.”

Mr. Levine was one of hundreds of Obama field staff members and volunteers who fanned out at a dozen gay pride celebrations across the country over the weekend with a meticulous set of marching orders from the Chicago campaign headquarters: Get names, cellphone numbers, and e-mail and home addresses. But most important, get commitments to volunteer.

At times, the parades could have been confused for Obama campaign rallies. In Chicago on Sunday, 300 of his campaign staff members and volunteers marched down Halsted Street through the heart of the gay district to chants of “Four more years! Four more years!” Along Fifth Avenue in New York, a group of about 200 Obama supporters who walked the parade route were cheered by crowds waving powder-blue “L.G.B.T. for Obama” placards, referring to the lesbian, gay, bisexual and transgender community. “Obama! Obama!” the onlookers cried.