Mount Pleasant, S.C. ? Democrat John Kerry formally launched his presidential candidacy Tuesday by offering his Vietnam War-hero credentials and Senate tenure as an alternative to President Bush’s record. His campaign at a political crossroads, he denied any shakeup was coming.

“Every day of this campaign, I will challenge George Bush for fundamentally taking our country in the wrong direction,” Kerry told the crowd. “George Bush’s vision does not live up to the America I enlisted in the Navy to defend.”

The stars-and-stripes announcement with the aircraft carrier USS Yorktown as a backdrop and Kerry’s wartime comrades at his side came amid talk of changes in the campaign. Kerry first said there were no plans “at this time” for changes, then gave a mixed review of his staff.

He then issued a terse statement after meeting with top aides.

“I have confidence in my campaign,” Kerry said. “I have assembled a great team that is going to beat George W. Bush, and any rumors to the contrary are completely erroneous and there will be no changes.”

Aides speaking on condition of anonymity said Kerry delivered that same message to top staffers in private. The distraction was the last thing Kerry needed on a day he hoped would be filled with the major themes of his campaign. The issue arose when he was questioned about looming changes.

Kerry said he had no immediate plans for an overhaul but gave his staff mixed grades.

“I think they’ve done a spectacular job on a lot of things. I think there were some things we could have done better,” Kerry said upon arriving in Iowa, the second stop on his announcement tour.

The four-term Massachusetts senator was once viewed as the Democratic front-runner in the crowded field of nine, but that perception evaporated in the heat of party rival Howard Dean’s summer surge.

Kerry’s political free-fall has prompted a fresh round of finger-pointing in his deeply divided campaign and has the candidate considering changes, according to several campaign officials who spoke on condition of anonymity.

Kerry said he has not considered a shake-up, though he sounded as if changes could be made.

“I always reserve the right to do what I need to do to run a good campaign,” he said.

Democrat John Kerry takes a standing ovation after formally announcing his candidacy to be president of the United States at Patriot's Point in Mount Pleasant, S.C. Kerry was joined by Gen. Steve Cheney, second from right, and his wife, Teresa Heinz Kerry, right, at Tuesday's announcement.