DUBUQUE, Iowa — Looking buoyant and rejuvenated by new polls showing him atop the Republican presidential field, Senator McCain of Arizona returned to Iowa yesterday to see if he can pull out a respectable showing in a state his campaign had all but written off.

“We are now obviously down to the wire,” Mr. McCain said, moments after a supporter, Senator Brownback of Kansas, announced the news about the recent surveys.

A crowd of a little over 100 gathered in an airplane hangar to hear Mr. McCain make his pitch, which focused on his national security credentials. “I have the knowledge, the experience, and the judgment to lead this nation,” he said.

Mr. McCain warned repeatedly about “the threat of radical Islamic extremism.” He said events such as the recent assassination of a Pakistani leader, Benazir Bhutto, serve to underscore the need for a president with a strong background in foreign affairs.

“Things happen that we don’t anticipate,” he said. “If I’d have been before this crowd three weeks ago and started talking about Pakistan, you’d have said, ‘What does that have to do with anything?'”

Mr. McCain cited the success of the troop surge in Iraq as evidence of his insight. “I was the only one who said the Rumsfeld strategy is going to fail. I was the only one who said the Petraeus strategy has got to be implemented,” the senator said. “I was criticized at the time for being disloyal.”

The Arizona senator also touted his lifelong crusade against pork-barrel spending. “We’ve got to stop it. It is corruption and I don’t use that word lightly,” he said.

Speaking with reporters, Mr. McCain said he is unfazed by negative ads he is facing in New Hampshire from another candidate, Mitt Romney.

“I’m kind of flattered that he would continue these attacks against me,” the senator said. “That’s just the kind of campaign he runs and I am confident that people will reject that kind of negative campaigning.”

Asked why his once-moribund campaign seems to be surging in the polls now, Mr. McCain said, “I think just because I tell the truth.”

He also said the national security issues are “coming to the fore here.”

A local supporter of Mr. McCain, Ken Green, said he was “impressed” by the comments Mr. McCain made immediately after Mrs. Bhutto’s assassination. “That … made all the other candidates seem wishy washy,” he said.

Mr. McCain said he was enjoying the apparent boost and had no inclination to revisit the mistakes which led his campaign into the doldrums. “If I had it to do over again, I wouldn’t want to,” he joked.”