Ron Paul says he could "explode" and his supporters believe he can win the GOP presidential nomination. But the Texas congressman is ruling out a third-party bid if he's not the Republican nominee.

Paul was the guest at a breakfast for reporters hosted by the Christian Science Monitor. USA TODAY's Susan Page was there, and she reports Paul had much to say about the GOP field, his standing and his impact on the policy debate.

Paul, who lags behind Rick Perry and Mitt Romney in most national polls on the race, said he's "not considering" a third-party bid if he doesn't win the GOP nod.

It's very hard, the 1988 Libertarian Party presidential nominee says, "unless you're a billionaire. Money talks."

Paul says he's pleased that the GOP has moved significantly since his 2008 race and notes that issues where he was once a lone wolf -- such as reining in the Federal Reserve Board and getting troops out of Afghanistan -- are now the norm.

"Who would have believed after 100 years we would be talking about the Federal Reserve at debates? I mean, this is fantastic from my viewpoint," Paul says. "I'm glad it's out there."

Paul credits successes to the Internet and social media, where he has a strong following. He says it's "premature" to discuss which GOP rival would get his support, should he not win the nomination. But he vows his supporters will make a difference.

"I think our delegates will not be insignificant, and they will play a role one way or the other," the Texas congressman says.