DAYTONA BEACH, Fla.—Mitt Romney accused President Barack Obama of running a campaign based on "petty attacks" and "silly word games" and accused his rival of having "no agenda" for the future.

"The Obama campaign has become the incredible shrinking campaign," Romney said at an oceanside rally here with his running mate, Rep. Paul Ryan. "This is a big country with big opportunities and big challenges. And they keep talking about smaller and smaller things."

Romney's remarks appeared to be a response to Obama's charge Friday that the Republican nominee is suffering from "Romnesia" in distancing himself from his past policy positions.

Speaking to a crowd of several thousand people here, Romney turned the tables on his Democratic opponent, repeating his claim that Obama has laid out no specifics about what he would do if elected for a second term in the White House.

"Have you been watching the Obama campaign lately? It's absolutely remarkable. They have no agenda for the future. No agenda for America. No agenda for a second term," Romney said. "It's a good thing. They won't have a second term."

Romney insisted his campaign has "big ideas and bold ideas" and a "strong agenda."

Even as Romney and his running mate attracted a large crowd, Obama supporters could be heard in the distance chanting louder and louder—aiming to disrupt the GOP event. At one point, a man emerged on a hotel balcony overlooking the Romney-Ryan rally site and shouted, "OBAMA!!!"

This is Romney's last public event before Monday's final presidential debate in Boca Raton—about 200 miles south of here. The GOP nominee will spend Saturday and Sunday doing debate prep in Delray Beach, which is near the debate site.