WASHINGTON, Oct. 16 — On an overcast Friday morning last month, White House aides ushered an influential group of conservative radio hosts into the Oval Office for a private audience with the president.

For an hour and a half, Mr. Bush discussed his case for the war in Iraq, his immigration proposals and even the personality of his Scottish terrier Barney, who scratched on the door during the session until the president relented and let him into the office, according to several hosts who attended.

The meeting, which was not announced on the president's public schedule, was part of an intensive Republican Party campaign to reclaim and re-energize a crucial army of supporters that is not as likely to walk in lockstep with the White House as it has in the past.

Conservative radio hosts are breaking with the Republican leadership in ways not seen in at least a decade, and certainly not since Rush Limbaugh's forceful advocacy of the party in 1994 spawned a new generation of stars, said Michael Harrison, publisher of the industry's lead trade publication, Talkers.

Disgruntlement can now be found not only among the more flamboyant radio voices, like Michael Savage, who raged against Mr. Bush's proposals on immigration and other issues, but also among more mainstream hosts, like Laura Ingraham, who told her listeners in the wake of the scandal involving former Representative Mark Foley and under-age Congressional pages, "You have to ask yourself, the people who are in positions of power now in the Republican Party, are they able to credibly articulate the conservative agenda to the American people — to rally the base, to rally the country?"

Such questions, coming from such quarters, have created yet another challenge for the White House and the central party leadership as they work to steer Republicans to victory next month in the face of low approval ratings and dissatisfaction among the party faithful.

Strategists on both sides agree that the party's greatest hope for holding control of Congress now rests with its ability to get core Republicans to vote, and that talk radio, which reaches millions of them, is crucial to the task.

Democratic strategists say talk radio remains a fearsome Republican advocacy force for which they have little direct answer. (Air America, which features liberal hosts, including Al Franken, filed for Chapter 11 bankruptcy last week.) The top two rated conservative hosts, Mr. Limbaugh and Sean Hannity, have done more than their part to rally their listeners this year, especially during the Foley scandal, to the great relief of Republican Party officials. And even those critical of Mr. Bush or the party on specific issues still consider themselves major supporters in general, with perhaps the exception of Mr. Savage.

But Mr. Savage is the third most popular host in the nation, with at least eight million listeners weekly, according to Talkers. And the Democrats have watched happily as he and others have at times sent reverberations of conservative frustration into what they often call the "Republican echo chamber."

The challenge now falls to party strategists to persuade the hosts to overcome the frustrations of many hard-core listeners over issues like spending and border security without alienating them.

"When conservatives are agitated at the president, radio hosts feel pressured to stand with the conservatives against the president to prove their independence," said Tim Graham, an analyst at the Media Research Center, a conservative news monitoring group. But, Mr. Graham said, "realizing what life would be like if we lost the House is concentrating people's minds."

The White House and the Republican National Committee are hammering home that point in interviews, talking-point bulletins and a healthy dollop of pomp that only a White House can provide.

The effort will peak on Oct. 24, when the administration will hold something of a talk-radio summit meeting, inviting dozens of hosts to set up booths on the White House grounds, where top cabinet officials are expected to sit for interviews.

The party chairman, Ken Mehlman, has already been working overtime on the talk radio circuit. From Wednesday to Friday of last week, he was interviewed a total of 20 times in Missouri, Tennessee and Ohio, promoting party stances on tax cuts and terrorism.

But, several hosts said, the most telling development so far this year was the White House decision to invite some of the most popular hosts to the Oval Office for off-the-record time with the president.

Kevin Sullivan, the White House communications director, said the meeting was among the latest examples of the administration's effort to put Mr. Bush in front of more news media as his own best spokesman. The president also gave interviews recently to several television anchors and held an Oval Office chat with a group of conservative writers.

And Mr. Bush granted an on-camera interview to Bill O'Reilly of the Fox News Channel. The first of three parts ran Monday night.

Still, officials said, the meeting with the radio hosts gave Mr. Bush a chance to speak intimately with a group that reaches an overwhelmingly Republican audience of 30 million people per week.

"You want to make sure that your friends are friendly," said Tony Snow, the White House press secretary, who has been crucial to the effort and who was a conservative radio host who turned harshly critical of Mr. Bush just months before he went to work for him last spring.

Mr. Snow said that while "any party has its disagreements," there was little division among Republicans on the top two issues Mr. Bush has tried to push this year: terrorism and taxes.

And the fight against terrorism dominated the discussion at the meeting.

"This was clearly, clearly an effort to kind of rally the troops when the troops need rallying," said Mike Gallagher, who attended the meeting and whose daily program reaches at least 3.75 million people each week. "They know that we've got an audience of people who may or may not be on the political fence right now."

Mr. Gallagher said that he and the other hosts — Mr. Hannity, Ms. Ingraham, Neal Boortz and Michael Medved — talked about the experience on their programs "for days and days and days."

(Mr. Limbaugh said that he met with Mr. Bush and Karl Rove, the president's chief strategist, in the Oval Office in June, but generally tried to keep his distance to maintain independence.)

On his Web site, Mr. Medved wrote how Mr. Bush spoke about his commitment to his immigration plan in terms of the fight against terrorism. He said the president made a case that if he were to give in to conservative complaints, "the nation's enemies (and the rest of the world) would take away the belief that the president could be bullied, prodded, overwhelmed and intimidated."

Mr. Hannity said of the meeting, "I think he'd have an 80 percent approval rating if he could bring people into the Oval Office six people at a time and explain it all to them."

But Ms. Ingraham, who recently went bike riding with the president, has continued to complain about federal spending, progress in Iraq and, lately, the Republican leadership's handling of the Foley scandal. Ms. Ingraham likened herself to a sports fan who nonetheless has occasional criticism of the coach. But, she said pointedly on her show: "I am not an advocate for the G.O.P. I'm an advocate for conservative ideas."

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