LOS ANGELES (CNN) -- Sen. John McCain insisted Wednesday he is happy with his presidential campaign despite staff shake-ups, fundraising woes and stagnant poll numbers.
"As soon as people start focusing on the race, we're going to win the nomination," Sen. John McCain said.
The Arizona Republican also said he still expects that as the "most prepared" candidate, he can win the GOP nomination.
"There's ups and downs in every campaign I've ever been in. I've made mistakes many times in my political career, and I've always corrected them," McCain told CNN chief national correspondent John King.
"We're going to be just fine. As soon as people start focusing on the race, we're going to win the nomination."
McCain, who has been a staunch supporter of the war in Iraq, also said he opposes a call by Sen. John Warner of Virginia to withdraw some U.S. troops by Christmas. Warner, a leading Republican voice on defense issues, wants to send the message that the American presence in Iraq will not be indefinite.
"It's a bad idea, a terrible idea, and I'll fight it every step of the way," McCain said. "John Warner and I are very close friends, but that sends the signal to al Qaeda and bad people in the region that we're leaving, and that's not our position. Our position is we're going to succeed." Watch McCain explain his views in an exclusive interview »
McCain spoke to King on his 71st birthday, which makes him not only the oldest candidate in the race but would also make him, if he wins the White House, the oldest person elected to the nation's highest office. The Arizona senator said he thinks his experience will keep him viable.
"The people of this country want experience. They want knowledge, and they want leadership. And I've been involved in that all my life," McCain said. "I'm the most prepared to take on the transcendent challenge of the 21st century, and that is radical Islamic extremism."
"I need no on-the-job training. I'm fully prepared to meet that challenge."
A year ago, McCain, who ran a spirited race against then Texas Gov. George W. Bush for the Republican nomination in 2000, was seen as the front-runner for his party's White House nod. But amid his support for the increasingly unpopular Iraq war and a controversial immigration reform bill, he's fallen back in the pack.
An average of four national polls taken in July had McCain's support at 15 percent. That puts him well behind former New York Mayor Rudy Giuliani, at 30 percent, and former Tennessee Sen. Fred Thompson. Thompson polled at 19 percent, although he has not officially entered the race.
McCain has been one of the chief champions of the immigration reform bill, which has put him at odds with many conservatives in the GOP base whose support will be key to securing the nomination. The senator told King he is convinced the bill won't get through Congress unless the American people are convinced security will be beefed up on the nation's borders.
"I'm still for comprehensive immigration reform, but Americans have to have the assurance that we have secured the borders," he said. "I promise to do that. I will secure the borders, then we will move on to other things. That's the message of this last debate. I got it.
"Secure the borders first -- that's the lesson, and that's also got to do with trust and confidence, which I think I can restore with the American people." E-mail to a friend