U.S. Sen. John McCain, R-Ariz., stands with his wife, Cindy, as he speaks during a news conference Thursday at the Statehouse in Des Moines, Iowa. McCain fired up the Straight

Des Moines, Iowa ? John McCain fired up the “Straight Talk Express” bus from his first presidential campaign Thursday in hopes of getting his second bid back on course after an early-season slump.

“We’ve got to build the momentum,” the Republican senator said, even as he brushed off polls that show him trailing rival Rudy Giuliani. “I’m very happy with where we are right now. We’re fine.”

Still, McCain said of his overall effort to launch a national campaign: “We haven’t done a great job, but we’ve done a pretty good job in doing what’s necessary to prepare.”

Nine months before the first GOP primary contests, McCain embarked on a two-day bus tour of Iowa and told reporters traveling with him that there was plenty of time to recapture the magic from the 2000 race. He likened this stage of the campaign to spring training, a warmup for the regular season, and said he was confident he would win over voters as he steps up campaigning.

The four-term Arizona senator started this campaign as the perceived Republican front-runner, leading in the race for political talent, endorsements and proven fundraisers. He and Giuliani were virtually tied in most national polls last year, but the gap has widened during the past few months to double digits.

Instead of campaigning daily, McCain spent most of his time on Capitol Hill trying to sell President Bush’s unpopular Iraq troop-increase strategy to a skeptical Congress and a wary public. Giuliani, meanwhile, traveled the country seeking support and raising money.

McCain’s campaign suffered as Giuliani’s caught fire.

“The interesting story so far has been the complete descent of McCain,” said Steve Lombardo, a Republican consultant in Washington who attributed it in part to widespread disenchantment with Congress. “He’s a senator who is seen as a D.C. insider. It’s been a rough period of time for him. Right now, the public is just fascinated with Giuliani.”

Aboard his campaign bus, McCain shrugged off the polls and suggestions of a stalled effort.

“This is the first time we’ve been on the bus, but we’ve been working at this for well over a year,” McCain said. “We’ve been trying to lay the political and financial base.”

McCain said Bush’s legacy – and to some extent his – will be shaped in large measure by what happens in Iraq.

“I would think that I am going to be judged at least somewhat by it,” McCain said on his bus. “The irony of ironies, I was the biggest complainer about the way it was being conducted at the time, but life is not fair.”

Republicans who have backed McCain privately fret that the campaign is burning through money at an alarming rate by building an overly bureaucratic organization – in effect overcompensating for a campaign weakness from 2000. They express concern that McCain doesn’t appear to be the “Happy Warrior” he was then and may be having difficulty making the transition from an underdog to an establishment candidate.

“My positions haven’t changed,” said McCain, 70. “I’m too old to change. I’m the same. People will understand that as the campaign goes on.”

McCain’s bus tour took him first through Iowa, an early voting state that he bypassed seven years ago.

He gets on another bus this weekend in New Hampshire, where he won the 2000 primary before ultimately losing the GOP nomination to George W. Bush.

McCain met privately with Iowa legislators and then traveled through the state for a few question-and-answer sessions with potential voters.