(CNN) The Republican establishment is making the most of the chance it had long sought to finally say this to Donald Trump: You crossed the line.
Ever since announcing his presidential run last month, the brash, unfiltered billionaire businessman has created headaches for the party. Particularly, his comments equating some Mexican immigrants to rapists and criminals left GOP leaders struggling to appease those Trump had offended without alienating conservative voters attracted to his views on combating illegal immigration.
But on Saturday, Trump seemed to hand party bosses and the pack of 2016 Republican presidential candidates a golden chance to take him down at almost no political cost -- while making themselves look magnanimous. The spark for the latest political firestorm came when the New York real estate billionaire questioned on Saturday whether Arizona Sen. John McCain, a Vietnam War veteran who languished in a prisoner of war camp for more than five years, was a genuine "war hero because he was captured."
"I like people that weren't captured, OK?" Trump said, drawing gasps and "boos" from a conservative crowd in Iowa.
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What transpired within minutes of those inflammatory comments was telling. The GOP pile-on was swift and outspoken. McCain might be a controversial figure with plenty of enemies in Washington but he's universally regarded as a rare example of pure heroism.
The Republican National Committee, which stays neutral in the GOP primary and rarely weighs in on political debates, made the unusual move of publicly condemning Trump's remarks.
"There is no place in our party or our country for comments that disparage those who have served honorably," RNC spokesman Sean Spicer said on Twitter.
While the GOP was shy in responding to Trump's tirade against Mexico, it became clear on Monday that the party's hierachy was not going to be bitten by the Donald again.
"Right now what you are seeing is the party taking a dramatic shift this weekend -- taking Donald Trump head on," Mitt Romney's former senior political advisor and CNN contributor Kevin Madden told Wolf Blitzer. "This is their chance to really draw some stark contrasts about the direction of the party. This is an opportunity for a lot of these candidates."
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One after another, Trump's fellow GOP presidential candidates were quick to go after the former host of the reality TV show, "The Apprentice."
"Enough with the slanderous attacks," former Florida Gov. Jeb Bush tweeted. South Carolina Sen. Lindsey Graham, a close friend of McCain's, said Trump had "crossed a line today that will offend most every one that I know," and predicted that American voters would only have this message to Trump: "You're fired."
Florida Sen. Marco Rubio said that Trump's shot against a man who refused to take early release from the infamous Hanoi Hilton prison because his comrades could not come too disqualifed the billionaire as a potential commander in chief.
Former Texas Gov. Rick Perry, an Air Force veteran -- who is languishing in the polls and needs every headline he can get -- upped the ante -- calling on Trump to "immediately withdraw" from the 2016 race altogether.
Trump, by alienating sectors of the GOP electorate, is already breaking all the normal political rules, so it's not surprising he didn't choose to return to the high ground. True to form, he decided to intensify the row rather than walk away, or simply apologize, penning an opinion piece in USA Today, that was scathing of the media, the "establishment" and McCain.
"The reality is that John McCain the politician has made America less safe, sent our brave soldiers into wrong-headed foreign adventures, covered up for President Obama with the VA scandal and has spent most of his time in the Senate pushing amnesty. He would rather protect the Iraqi border than Arizona's," Trump wrote.
One Republican candidate chose not to join the torrent of criticism of Trump. Texas Sen. Ted Cruz was effusive in praise of McCain, who once called him a "wacko bird" but trod carefully on Trump, possibly hoping to appeal to the billionaire's supporters should he eventually exit the race.
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"I recognize that folks in the press love to see Republican-on-Republican violence, and so you want me to say something bad about Donald Trump, or bad about John McCain or bad about anyone else," he said. "I'm not going to do it."
Hillary Clinton, enjoying a rare moment out of the political spotlight, also took a chance to have a shot at the "hate (Trump) is spewing" towards Mexicans and stood up for her old Senate buddy McCain.
Even the Obama White House, no friend of McCain, pounced on the opportunity to fan the flames of a controversy that Democrats hope will damage the Republican political brand. Spokesman Josh Earnest praised McCain's "remarkable" service.
The GOP's swift and nearly unanimous criticism of Trump's remarks about McCain was particularly striking in light of how the party dealt with an earlier political row set off by his highly controversial comments -- even if it marked an easy political choice.
In his presidential announcement speech last month, Trump said that some people entering the United States from Mexico were "rapists," "criminals" and "drug dealers." The comments flew in the face of the GOP's desperate need to improve its standing with the increasingly influential demographic of Hispanic voters which are vital in general election swing states like Florida, Nevada and Colorado.
The episode suggests that though candidates like Bush and Rubio know very well the perils of estrangement from the community, they are not yet at ease with the base of their own party, which remains vociferously opposed to any immigration reform that would bring millions of illegal immigrants -- eventually -- into the U.S. fold.
More immediately, there is increasing speculation on whether Trump's broadside against McCain would turn out to be the moment when the billionaire's political bubble bursts -- in a way that would offer some relief to the GOP leadership.
Immediate evidence -- in the form of a new poll of Iowa voters -- was inconclusive, though it may be several days before the true impact of his remarks plays out. A survey by Monmouth University published Monday put Trump in second place in the first in the nation caucus state, at 13%, nine points behind Wisconsin Gov. Scott Walker. The poll did not find any significant change in support in interviews that took place after Trump unloaded on McCain.
A new ABC/Washington Post National poll on Monday had Trump leading the Republican field on 24% but his number dropped into the single digits in samples taken on Sunday following his McCain comments, albeit in a small sample size.
Madden predicted that Trump's bombast would indeed sooner or later begin to take a toll on his poll numbers.
"It's the beginning of the end -- part of the process. This information is going to start to get to voters," he said. "They are going to see a revelation in his character right now as well as his temperament that is going to lead them to look at other candidates."
While it could be the case that Trump's remarks could narrow what many analysts already think is a virtually non-existent path towards the GOP nomination, that doesn't necessarily equate to an early exit for the reality show star.
For now, the McCain clash seems to leave Trump where he most likes to be -- in the middle of a raging storm of publicity generated by himself about himself, while taking shots at the media and the Republican political establishment. It's the kind of behavior that gave his presidential run a fast start among a certain sector of the Republican electorate in the first place.