The GOP establishment is growing increasingly agitated that Donald Trump appears to be cruising to the nomination, yet mainstream Republicans lack a concerted, well-funded attack plan four months after he leapt to the top of the polls.
A handful of scattered, uncertain efforts to try to stop Mr. Trump—one super PAC recently compared him to a hippopotamus—have failed to dent his popularity. And a number of 2016 rivals and GOP leaders appear reluctant to wage war with Mr. Trump for fear of alienating his supporters, with both Senate Majority Leader Mitch McConnell (R., Ky.) and House Speaker Paul Ryan (R., Wis.) deflecting questions Sunday about the electoral fallout from his proposal to bar Muslim immigrants from the U.S.
None of the major Republican donors have invested in an anti-Trump campaign, with Las Vegas casino magnate Sheldon Adelson calling Mr. Trump “charming,” after a meeting last week, according to Reuters. Hedge-fund manager Paul Singer, who has endorsed Florida Sen. Marco Rubio, declined through a representative Sunday to comment on Mr. Trump.
“If donors continue to sit on the sidelines, they will be party to the election of Donald Trump as the Republican nominee and the election of Hillary Clinton as president,” said media consultant Rick Wilson, who is allied with super PACS backing Mr. Rubio and opposing Mr. Trump. “We’re talking about a political apocalypse if this guy is the nominee.”
Mr. Trump’s supporters, however, argue the New York businessman will boost GOP turnout in 2016 by energizing disgruntled voters who haven’t participated in recent elections. Any efforts by prominent Republicans to undercut Mr. Trump, they say, will only solidify support from the antiestablishment voters already in his corner.
“It’s a hard math equation to go after Trump and at the same time, pry him from his supporters,” said Republican consultant Susie Wiles, who is co-chairing Mr. Trump’s campaign in Florida. “The result is these one-offs that individually and collectively are not the dragon slayer that they hope. “
Many Republicans have speculated Mr. Trump’s campaign would implode on its own, without outside attacks. Yet he has led the polls nationally and in New Hampshire, which hosts the first primary, since late July. The only early-voting state where Mr. Trump has been knocked out of first place is Iowa, where Texas Sen. Ted Cruz surpassed him in four surveys this month.
One of the first attempts to damage Mr. Trump came in the fall from the Club for Growth, which aired $1 million in television ads in Iowa. But the spots from a group disliked by many donors for attacking centrist Republicans came and went with little to no impact on Mr. Trump’s popularity.
The two candidates most critical of Mr. Trump—former Florida Gov. Jeb Bush and Ohio Gov. John Kasich—are also among the least popular in the GOP field, with a combined 7% of support nationwide, according to the Real Clear Politics polling average.
“Someone needs to call him out,” Mr. Bush, who called Mr. Trump a “jerk” while campaigning Saturday in New Hampshire, said in a Sunday interview on CBS’s “Face the Nation.”
The super PAC backing Mr. Bush, Right to Rise USA, has released two television ads highlighting Mr. Bush’s broadsides against Mr. Trump in last week’s debate. “One candidate tough enough to take on the bully,” the ad says. “One candidate tough enough to take on ISIS.” The super PAC behind Mr. Kasich, New Day for America, also announced it would spend $2.5 million on anti-Trump ads.
Stuart Stevens, a top adviser to 2012 nominee Mitt Romney, said the well-funded super PAC behind Mr. Bush should have started attacking Mr. Trump months ago.
“No one has dumped serious negative advertising on Donald Trump,” he said. “If that super PAC had been attacking Donald Trump as they should have, it’s hard to imagine he would still be a factor in this race.”
Candidates who have been rising in the polls, however, have been trying to appease Mr. Trump and even demeaned his critics.
New Jersey Gov. Chris Christie, who recently defended Mr. Trump as a “serious candidate,” suggested Sunday that Mr. Bush was being hypocritical. “I stood right next to him at the debate and he said you can’t insult your way to the presidency,” Mr. Christie said in New Hampshire, repeating Mr. Bush’s words against Mr. Trump.
Meantime, Mr. Cruz never directly answered a question in last week’s debate about criticizing Mr. Trump at a private gathering but not in public. “He’s just fine,” said Mr. Cruz said.
And a proposal to kick Mr. Trump out of the New York Republican Party hasn’t made any headway.
“Polling done in the year before the primaries has not been very predictive of what actually happens, but I don’t discount that Trump has a big following and that this is an extremely unusual year,” said former Mississippi Gov. Haley Barbour, who served as chairman of the Republican National Committee. Of Trump as the nominee, he said, “Certainly, it’s a possibility.”