After a turbulent week that included disclosures about Gov. Sarah Palin and signs that Senator John McCain was struggling to strike the right tone for his campaign, Republican leaders said Saturday that they were worried Mr. McCain was heading for defeat unless he brought stability to his presidential candidacy and settled on a clear message to counter Senator Barack Obama.

Again and again, party leaders said in interviews that while they still believed that Mr. McCain could win over voters in the next 30 days, they were concerned that he and his advisers seemed to be adrift in dealing with an extraordinarily challenging political battleground and a crisis on Wall Street.

The expressions of concern came after a particularly difficult week for Mr. McCain. On Friday night, new questions arose about his choice of Ms. Palin as his running mate after an investigation by the Alaska Legislature concluded that she had abused her power in trying to orchestrate the firing of her former brother-in-law, a state trooper.

“I think you’re seeing a turning point,” said Saul Anuzis, the Republican chairman in Michigan, where Mr. McCain has decided to stop campaigning. “You’re starting to feel real frustration because we are running out of time. Our message, the campaign’s message, isn’t connecting.”

Tommy Thompson, a Republican who is a former governor of Wisconsin, said it would be difficult for Mr. McCain to win in his state but not impossible, particularly if he campaigned in conservative Democratic parts of the state. Asked if he was happy with Mr. McCain’s campaign, Mr. Thompson replied, “No,” and he added, “I don’t know who is.”

In Pennsylvania, Robert A. Gleason Jr., the state Republican chairman, said he was concerned that Mr. McCain’s increasingly aggressive tone was not working with moderate voters and women in the important southeastern part of a state that is at the top of Mr. McCain’s must-win list.

“They’re not as susceptible to attack ads,” Mr. Gleason said. “I worry about the southeast. Obama is making inroads.”

Several party leaders said Mr. McCain needed to settle on a single message in the final weeks of the campaign and warned that his changing day-to-day dialogue — a welter of evolving economic proposals, mixed with on-again-off-again attacks on Mr. Obama’s character — was not breaking through and was actually helping Mr. Obama in his effort to portray Mr. McCain as erratic.

“The main thing he needs to do,” said Vin Weber, a former Republican congressman from Minnesota, “is focus on a single message — a single, concise or clear-cut message, and stick with that over the next 30 days, regardless of what happens.

“He’s had a lot of attack lines. But it’s time to choose.”

John C. Danforth, a retired Republican senator from Missouri, said Mr. McCain should turn his attention mainly to drawing contrasts with Mr. Obama and “essentially go back to the basics.”

“I don’t think it’s enough to talk about earmarks incessantly,” Mr. Danforth said. “He’s made that point. You’ve got to get beyond that and talk about the very dramatic taxes and spending in the Obama program.”

Even that might not be enough, Mr. Danforth said. “This is a year where everything that could go in Obama’s favor is going in Obama’s favor,” he said. “Everything that could go against McCain is against him. It’s absolutely the worst kind of perfect storm.”

Mr. McCain’s advisers said they remained confident of victory.

“My sense of where things are: John McCain beat back what was a political climate that would have snuffed out any other candidate in the Republican Party,” said Nicolle Wallace, a senior adviser. “He’s beat back every hurdle that was ever placed in front of him.”

Mr. McCain acknowledged the challenge Saturday as he campaigned in Iowa, where President Bush won narrowly in 2004 but where polls show Mr. Obama with a healthy lead.

“I’d like to remind you that the political pundits have been wrong several times,” Mr. McCain said, “and they’re wrong because we will win the state of Iowa in November.”

Yet there were continued signs of confusion and turmoil in the McCain campaign, as his aides wrestled with conflicting advice, daunting poll numbers and criticism from state party leaders increasingly distressed with the way the campaign has been run.