COLUMBUS, Ohio (AP) --Tens of thousands of graduates, family and friends persevered through long security lines for an Ohio State University commencement ceremony Sunday with the U.S. president as the featured speaker.

President Barack Obama urged graduating students to be active citizens, to fight for causes they believe in, and to be better than generations before them. More than 10,000 students were receiving degrees, including 130 veterans, with tens of thousands more audience members in a crowd estimated at nearly 60,000.

Lines of ticketholders had wrapped around Ohio Stadium on the breezy, 70-degree day as people passed through metal detectors and bag checks amid security heightened because of the president's visit and increased caution after the Boston Marathon explosions.

Graduates went through screening at various gathering areas and paraded into the stadium through routes cordoned off by tall wire fences. Local police, state troopers and Secret Service agents were among the security forces on hand.

Some attendees acknowledged security was on their minds, in the aftermath of the marathon explosions, as they headed to see the president at such a large venue.

"You just never know," said Tharnjeet Bir, 22, a Capital University student attending to support a graduating friend. "There's stepped-up security everywhere, and stuff still happens."

Collin Shaum of Mansfield noted the visible presence of officers as he prepared to watch his girlfriend graduate. Shaum, 25, said he was feeling "safe-ish — as safe as one can be in a crowd of 80,000."

His girlfriend's mother, Connie Shaffer, 52, of Shelby, said she was a little nervous but never considered not seeing her daughter's graduation.

"If she's going to be here, we're going to be here," she said.

Suzanne Deming, the great-aunt of a graduate, said she'd seen snipers at the stadium and felt "very safe, no hesitation at all."

Some waiting graduates passed the time in line Sunday morning by exchanging Twitter messages with the hashtag "ThingsShorterThanOSUCommencementLine," with suggestions such as the sign-up line for space travel and the shelf life of Twinkies.

Lindsey Crump, a graduate in aerospace engineering, said she stood in one line of students for more than an hour before she realized she needed to check in at a different building. Crump said she had voted for Obama and was hoping to hear words of hope, not partisanship.

"I don't want to hear anything political," she said. "I want to hear something optimistic."

Obama challenged the graduates to "do better."

"Only you can make sure the democracy you inherit is as good as we know it can be," he said.

It address marked the Democrat's fifth trip to Ohio State since the start of 2012. He kicked off his re-election campaign with a rally there a year ago. He carried the battleground state twice.

The university said he was the third sitting president to deliver its commencement address. The others were Presidents George W. Bush in 2002 and Gerald Ford in 1974.