Has America gone nuts? Could Republican frontrunner Donald Trump really become president?

For two serene months after Donald Trump announced in March that he was forming a presidential exploratory committee, he failed to register in national political polls. People basically thought he was kidding.

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Then something funny happened. Trump, the developer and reality TV star, began hiring staffers in early voting states. He travelled to political rallies. He held a campaign launch event. And his poll numbers began to climb.

Now Trump has climbed all the way to the top. In three of the last four major national political surveys, Trump is the leader in the race for the 2016 Republican presidential nomination. A Fox News survey this week had Trump ahead of the Wisconsin governor, Scott Walker, 18-15, with Jeb Bush third. Thousands of enthusiastic citizens have been flocking to Trump rallies, from Arizona to New Hampshire.

The effect of Trump’s controversial weekend attack on 2008 presidential candidate John McCain , over his time in captivity in Vietnam, remains to be seen. But should Trump ride out the storm – as he has flourished in the squalls stirred up so far – the question will have to be asked.

Has American politics collapsed? Has the Republican party lost its collective mind? Is the Trump “surge” for real?

Veteran observers of US politics counsel calm, predicting that Trump will dazzle for a bit and then fade. With 16 months to go until election day and many voters doing everything they can to avoid political news, it’s too early, analysts say, for polling numbers to mean much. In the turbulent 2012 Republican nominating race, they point out, the so-called “lead” was passed among at least four non-competitive candidates before settling on eventual victor Mitt Romney.

Rick Wilson, a veteran Republican political consultant, said Trump was experiencing “a celebrity political bubble”.

He is a clown in a fancy hat, strutting the stage for a few minutes, and then the serious actors will come on the stage

Rick Wilson

“This is a guy who obviously, on every axis, is not a serious candidate, but who has touched a combination of factors – he’s got a lot of built-in name ID and celebrity from being on television for 20-plus years, and being a known public quantity for 20-plus years,” Wilson told the Guardian. “He’s struck a few chords with the immigration stuff, and he’s managed to capture the most valuable asset in a campaign, which is the attention of the press.

“He is an entertainer. He is a showman. He is a clown in a fancy hat, strutting the stage for a few minutes, and then the serious actors will come on the stage in a little while.”

While Trump may not have a chance of winning the Republican nomination, however, party leaders have warned that he could disrupt the Republican selection process. The potential problem, for the GOP, is that Trump has gained in the polls by saying divisive things, particularly on the topic of immigration .

“[Mexico] are sending people that have lots of problems, and they are bringing those problems to us,” Trump said at his launch event. “They’re bringing drugs. They’re bringing crime. They’re rapists … They’re sending us the worst people”.

The rhetorical bomb-throwing has activated a hard-right faction in the party who are excited to hear their anti-immigration views broadcast and who would embrace an intra-Republican war over immigration and other issues. That war could threaten the GOP bid to make inroads with Hispanic and Latino voters, and with other centrist voters. And such a failure could make the road to the White House an uphill climb.

Related: Donald Trump may have overstated his appeal among Hispanic voters, poll finds

In an apparent attempt at damage control, the Republican national committee chairman, Reince Priebus, called Trump last week to tell the candidate to “tone it down”, NBC News reported. Trump denied the report on Twitter.

“Totally false reporting on my call with @Reince Priebus,” Trump wrote . “He called me, 10 minutes, said I hit a ‘nerve’, doing well, end!”

But other Republican leaders and candidates are joining the call for Trump to zip it. McCain, who faces re-election next year, told the New Yorker this week that a large rally Trump held in Phoenix, in which the candidate appeared onstage with the father of a man who was killed by an undocumented migrant, was “very hurtful to me”.

“Because what he did was he fired up the crazies,” McCain said.

Even before his remarks on Saturday, Trump responded characteristically.

“The thousands of people that showed up for me in Phoenix were amazing Americans. @SenJohnMcCain called them “crazies” – must apologize!” Trump tweeted . “ @SenJohnMcCain should be defeated in the primaries. Graduated last in his class at Annapolis – dummy!”

The former Texas governor and current White House hopeful Rick Perry, who is lagging in the polls and could use some publicity, also squared off with Trump.

“I have a message for my fellow Republicans and the independents who will be voting in the primary process: what Mr Trump is offering is not conservatism, it is Trump-ism – a toxic mix of demagoguery and nonsense,” Perry said .

Trump fired back: “[Perry] doesn’t understand what the word demagoguery means … He should be forced to take an IQ test before being allowed to enter the GOP debate.”

On Saturday, Perry released a strongly worded statement in answer to Trump’s attack on McCain, saying he should withdraw from the race immediately.

Erstwhile frontrunner Jeb Bush has weighed in, too. “I have a big disagreement with Mr Trump about his tone and what he’s saying because it’s not accurate,” Bush said on Thursday.

Trump, in turn, has lustily criticized the Bush political machine. “Why do people listen to clown @KarlRove on @FoxNews ?” Trump tweeted Wednesday. “Spent $430M & lost all races — a Bushy!”

Senator Lindsey Graham, another weak-polling presidential candidate, has said Trump’s candidacy is a “defining moment” for the party and called on Priebus to declare Trump persona non grata.

“I think he’s riding a wave of outlandish behaviour,” Graham said of Trump on NBC . “He’s a wrecking ball when it comes to policy, and the way he’s engaging the public is hurting the Republican party.”

Not every competing 2016 candidate is going after Trump, however. Ted Cruz, the Texas senator, told NBC News he was “a big fan of Donald Trump” and planned to meet with him.

“Ted Cruz called me,” Trump said in his version . “And I don’t know why I’m meeting him, to be honest, but I do have respect for him.”

Cruz followed the same course on Saturday, decrying “Republican on Republican violence” .

Related: Is Donald Trump the greatest meme generator that God has ever created?

The entire drama appears headed for a very public denouement in early August, when Trump is likely to appear onstage with the other candidates at the first Republican primary debate. Trump cinched his right to appear in the debates by hitting a campaign finance filing deadline on Wednesday with the Federal Election Commission.

Trump’s financial disclosure showed that he had raised $1.9m since entering the race a month ago. That included a $1.8m loan from himself – but Trump also had about 60 individual donors.

In a statement in advance of his filing, Trump claimed he was worth TEN BILLION DOLLARS, spelling the sum out in capital letters, and his team complained that the financial disclosure document was “not designed for a man of Mr Trump’s massive wealth”.

“This is a carnival seal,” said Wilson. “It balances a ball on its nose, and it’s very clever at doing that. It’s very clever at saying, ‘I’m so rich! I’m so rich! My fortune is huuuuge’ – and doing the whole Donald Trump act. At playing Donald Trump.

“At some point voters are going to say, is this a man whose finger I want on the button, is this a man who is actually going to go out and negotiate with countries that don’t like us on consequential things?

“This isn’t about badgering someone down on cost-per-square-foot. This is about real, consequential, life-and-death, existential challenges to our nation and others.

“And at the end of the day, Donald Trump is not a person who is a serious choice.”

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