(AP) -- Even campaigning half as much as his rivals, Donald Trump is drowning them out in an echo chamber of insults and charged pronouncements that have taken over the presidential campaign. Frustrated GOP candidates trekking across Iowa, New Hampshire and South Carolina are struggling to be heard.

All the while, some Republican officials worry the intense Trump focus is letting Democratic front-runner Hillary Clinton escape serious scrutiny as she works to strengthen her case to general election voters in the 2016 contest.

"He's playing you like a fine Stradivarius violin," former Florida Gov. Jeb Bush told reporters who mobbed him after a campaign stop in New Hampshire this week -- to get his reaction to Trump's remarks. "This is what he does. He's an expert at this. He's phenomenal at garnering attention."

Perhaps no one is more frustrated than Bush, the former Florida governor once thought the likely nominee but now fighting for relevance as Trump leads most Republican polls.

Bush spoke at length during his campaign stops about his strategy to stop the Islamic State, which he said President Barack Obama and Clinton, as secretary of state, had foolishly dismissed.

Yet the first question he faced from voters at a Tuesday night stop in southern New Hampshire had nothing to do with his policies. "I'm going to say two words, probably the last two words you want to hear right now," said Tim Chrysostom, one of 125 in attendance. "Donald Trump."

"What about him?" Bush replied curtly.

With Trump's call to ban Muslims from entering the United States, just the latest example of his provocative statements, the billionaire businessman has found a way to dominate the conversation even when he's not in the room.

On Wednesday, Bush touted a plan to return more power to states. Ohio Gov. John Kasich addressed national security in New York. And retired neurosurgeon Ben Carson outlined his plan to reshape the U.S. health care system.

Each made hardly a ripple in the race.

Trump's newest comments on Muslims, however, got attention.

"I'm doing good for the Muslims," he declared in an interview to be aired Wednesday night on CNN. "Many Muslim friends of mine are in agreement with me."

Tens of millions of dollars in campaign spending aren't helping Trump's adversaries break through.

Trump spent $5.6 million through the end of September. The rest of the GOP field spent more than $76 million over the same period.

Bush and his supporters alone have invested some $32 million in television and radio commercials. Trump? About $300,000.

Even Trump's critics, like New Hampshire Republican national committeeman Steve Duprey, admire the real estate mogul's ability to dominate the conversation with such a modest investment of time and money.

"No one can deny he's running a brilliant campaign," Duprey said.

Trump has all but abandoned traditional retail campaigning in which candidates court smaller groups of voters in key states. Instead he's focusing on massive rallies and most often on national media interviews -- frequently conducted on the phone from Manhattan's Trump Tower.

Extraordinary statements have become ordinary for Trump. At the same South Carolina rally where he read his no-Muslims statement aloud, he also suggested "closing that Internet up in some way," saying it had become a breeding ground for radicalization.

Some rivals have tried to emulate Trump's fiery rhetoric.

Texas Sen. Ted Cruz explained his preferred approach to the Islamic State militants by promising to rain violence on their strongholds. "We will carpet bomb them into oblivion," he said at a tea party rally in Cedar Rapids, Iowa, on Sunday. "I don't know if sand can glow in the dark, but we're going to find out."

At a rally Tuesday night in Atlanta, Carson suggested that U.S. citizens should train for terrorist attacks much as schoolchildren once conducted air-raid drills during the Cold War. "We need to start teaching people what to do once again in those situations," he said.

Such tactics concern some Republican donors and operatives.

"You're not going to get earned media unless you're outrageous, but it is foolish to try to out-Trump Trump," said John Jordan, a California donor backing Florida Sen. Marco Rubio.

At the same time, Republicans are missing a key opportunity to weaken vulnerable Democrats, GOP operatives say.

The Trump call to block Muslims from the U.S. abutted -- and then overtook -- criticism that Obama's White House address about fighting the Islamic State was weak. Questions about Clinton's use of a private email server while secretary of state have faded.

"Donald Trump is a massive walking, talking in-kind donation to former Secretary Rodham Clinton," said Liz Mair, a GOP strategist who is trying to raise money to curb a Trump rise. "Media focus on him, and the type of focus more specifically blocks other candidates who could better compete against her from getting any attention whatsoever."

In New Hampshire, Sheryl and Mark Poor say they are tired of Trump.

The Manchester couple hasn't settled on a 2016 candidate, and attended a Bush rally this week to learn more about him. That was hard to do with all the questions about Trump, Sheryl Poor said.

"I'd like to see Donald Trump go," she said. "He doesn't have the finesse, and he's going to upset the world."

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AP writers Steve Peoples and Jill Colvin contributed to this report.