President Barack Obama returned to Columbus for a campaign rally at Ohio State on the Oval Tuesday, the last day to register to vote in Ohio.

In his speech, Obama focused on the importance of education, and called education the gateway of opportunity.

“I believe that we should have the best education system in the world, bar none,” Obama said. “I got a great education because that’s what this country does.”

Obama took the podium at about 5:10 p.m. and spoke for about 20 minutes.

Throughout his speech, when Obama mentioned Republican presidential nominee Mitt Romney, he was met with boos from the crowd. But Obama told the crowd not to boo, to vote.

“If you give up on (the idea) that your voice can make a difference, then other voices fill the void,” Obama said.

Special guest will.i.am of the Black Eyed Peas took the stage at 4:30, DJing for the crowd, which he referred to as “Buckeye Peas.” He performed for about a half hour and talked about the importance of education during Bruce Springsteen’s “Born In The USA.”

The estimated 15,000 attendees surpassed the 14,000-person crowd at the Schottenstein Center in May when Obama kicked off his re-election campaign.

Obama last visited Central Ohio less than a month ago, for a campaign stop at Schiller Park in German Village Sept. 17. Romney was last in Columbus Sept. 26, when he visited Westerville South High School. 

Romney has not yet visited OSU, but his son Craig Romney was on campus Saturday.

Tuesday’s visit to the Oval was Obama’s fifth to Ohio State in two years.

Results of a Tuesday seven-day rolling Gallup poll of registered voters have Obama in the lead with 49 percent, and Romney trailing at 46 percent with less than a month until the Nov. 6 presidential election.

Obama’s remarks were preceded by short speeches from Columbus Mayor Michael Coleman, former Ohio Sen. John Glenn and Ohio Sen. Sherrod Brown.