MANCHESTER, N.H. - 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, once thought the likely nominee but now fighting for relevance as Trump leads most Republican polls.

On Tuesday, a New Hampshire poll, taken before Trump's comments on banning Muslims, showed his lead growing in the state, now at 32 percent, up from 26 percent in September. (Gov. Christie, meanwhile, who has campaigned hard in New Hampshire, has risen to third place, at 9 percent, up four points.)

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

Yet the first question he faced from voters at a Tuesday night stop in 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.

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.

And tens of millions of dollars in campaign spending aren't helping his rivals to 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 occasional massive rallies and most often on national media interviews - frequently conducted on the phone from Manhattan's Trump Tower or his private jet.

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

"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."