We should not be surprised that in such a period of unprecedented upheaval things are not as they seem. Take Garrison Keillor, a wonderful man of letters with whom we don't often quibble. In old London this week, Keillor paused on Grub Street, picturing Trump in the midst of the 17th-century crowd that hung there – "where hacks and scriveners hung out in the taverns, scribbling satire, polemics, poesy, political screeds, for measly pay, a band of misfits held in low esteem like the strumpets in the doorways. Nowadays, this crowd has found a happy home on the internet." Keillor reckons Trump would have been in his element in the tumult of that time: "He'd be magnificent in his great swirling robes, surrounded by courtiers and sycophants, ranting against the Puritans, supporting the monarchy, smiting his enemies. The problem in 2016 is that most of what he says is a lie." Writer and humorist Garrison Keillor. Credit:AP But we'd be wrong to fixate only on Trump's lies.

He has told plenty. But history will remember Trump for the unvarnished truth he has revealed about the Republican Party, about a toady leadership and manipulative, calculating donors who for decades abused the interests of a seething membership, believing they could always control the rabble – even as they imposed policies that sold them out. The more Trump called them out, the more they fell in around him, figuring they would bend him to their will or, as Senate Majority Leader Mitch McConnell reportedly told associates early this year: "We'll drop him like a hot rock." Now McConnell is in hiding. House Speaker Paul Ryan dithers – seemingly thinking he is inoculating himself and his congressional majority by not formally withdrawing his endorsement of Trump; while at the same time, he has made perfectly clear that he loathes the thin-skinned and vengeful New Yorker. With few exceptions, the whole congressional mob fell in with Trump – they would live with him because they had to. Those who challenged him for the nomination shelled out hundreds of millions for the privilege of curling up and dying. The Bush clan has been remarkable. When it came to pushback, the political star power of the father-and-son former presidents counted for naught and despite his "shock and awe" fundraising going into the primaries, Jeb Bush, the anointed one, lived up to Trump's taunt that he was "low energy".

Low energy: Jeb Bush. Credit:Frank Franklin One of the ironies of this campaign is that the only member of the Bush family who had a useful hand in tripping up Trump, wittingly or not, was George and Jeb's flaky cousin Billy Bush – the guy who hosts beauty pageants and Hollywood red carpet events, who sprung to unenviable prominence with his encouragement of Trump in the "grab them by the pussy" video. And what do we make of Texas senator Ted Cruz, the last man to fall over as Trump snatched the party's presidential nomination? It seemed he would stick to his principles, after he stood alone on the stage at the Republican convention in July, pretty well telling a party that was about to confirm Trump's nomination: "Don't do it!" But in the end he too capitulated – he dipped his lid to Trump. And now in the midst of a party-wide mutiny, Cruz perversely refuses to bolt. Describing this week's implosion of the Trump campaign and the existential crisis it heralds for the GOP in Congress and beyond, Ben Shapiro - a former staffer for the Breitbart news website that is an arm of the Trump campaign - opted for King Kong as a metaphor.

"This is the scene where the Republican Party thought they had captured King Kong and chained him; and they put him on stage for everyone to fear the awesome might of King Kong," he said. "And then King Kong breaks free and starts trampling people in the audience." Whether Trump wins or loses - the latter being the most likely outcome - this is a party in deep crisis. In the event that Trump wins, he has rejected whole slabs of GOP orthodoxy; in the event that he loses, he will become an insufferable opposition outside Congress, riling up the base and probably rendering the party impotent – remember more than 13 million voted for him in the primaries – as he casts himself as the sole opposition to a President Hillary Clinton. King Kong unleashed: Republican presidential candidate Donald Trump. Credit:AP From his eyrie at the Brookings Institution, conservative commentator Robert Kagan makes no attempt to conceal his contempt: "The current Republican Party is unfit to lead the country. It has failed the greatest test a political leader or party can face, and failed spectacularly – it has abandoned its principles out of a combination of cowardice and opportunism; it has worked to place in the White House the most dangerous threat to US democracy since the Civil War; and it has in the process engineered its own suicide." And of a leadership that he muses wants to be taken seriously as able to confront Moscow and Beijing, when it couldn't stare down Trump, he writes: "These are the people we're supposed to put in charge of the House and Senate for another two years? Whom we're then supposed to rally behind in the battle for the White House in 2020? No. Not this group. We know too much. We know all we need to know."

The Republican crisis is this deep – at a time when it is required to reinvent itself, an entire leadership generation has been discredited. As the veteran GOP strategist Steve Schmidt sees it: "Scores of Republican leaders have failed a fundamental test of moral courage and political leadership in not speaking truth to the American people about what is so obvious." GOP insider and Florida lobbyist John "Mac" Stipanovich is even more scathing: "Most Republican office-holders gritted their teeth and endorsed and even embraced Donald Trump … All of those people were collaborators, and all of those people will have to live with their collaboration for the rest of their political lives." Opinion on the party's very survival is divided, ranging from total collapse, to Trump peeling away his rump supporters, to God knows – if the Trump mob decamps, would there be enough left to call a party? Their guy: Donald Trump represents the Republican's restless middle class. Credit:AP Republican consultant and pollster Frank Luntz trawls history in a bid to calm fears, arguing that the party is more resilient than its internal critics believe: "The GOP has been through these rough elections before, and they have emerged stronger and more unified much more quickly.

"Watergate may have destroyed the GOP in 1974, but Reagan won by nine [percentage points] just six years later and by 20 [points] four years after that. The loss of George H.W. Bush in 1992 was supposed to be the end of the GOP, but they won the House and Senate for the first time in 40 years just two years later." Others anticipate more dramatic developments. Writing in The American Conservative, Rod Dreher wonders if the remnants of the party will start with a green fields site: "Trump may well have prepared the way … in the same way that a bomber squadron prepares the way for a shiny new factory by bombing the old one to rubble." It's early days – despite a deep sense of foreboding. But some of the most considered speculation on a way forward comes from David Frum, a neo-conservative and former George W. Bush speechwriter. Writing in The Atlantic, he gets to the nub of the hoax exposed by Trump: "White Middle Americans express heavy mistrust of every institution in American society: not only government, but corporations, unions, even the political party they typically vote for – the Republican Party of Romney, Ryan, and McConnell, which they despise as a sad crew of weaklings and sellouts. They are pissed off. And when Donald Trump came along, they were the people who told the pollsters, 'That's my guy.'" They responded to Trump's defence of what the French call "acquired rights" - health care, pensions, and other programs that benefit older people; his attacks on bankers and technocrats who demanded more and more austerity; against migrants who want "their" jobs; and against a globalised market that depresses wages and benefits.

"They lean Republican because they fear the Democrats want to take from them and redistribute to Americans who are newer, poorer, and in their view less deserving – to "spread the wealth around", in candidate Barack Obama's words ... Yet they have come to fear more and more strongly that their party does not have their best interests at heart." The Tea Party spoke for them but, says Frum, against all evidence, the GOP donor class interpreted the Tea Party as a movement "in favour of the agenda of the Wall Street Journal editorial page". A Trump supporter at rally in Florida. Credit:AP Despite the policy bent of the GOP leadership, most of them worry that corporations and the wealthy exert too much power and they don't have a problem with ripping more tax from the wealthy. The eruption of angry support for Trump was a response to the leadership's push to give these vested interests even more power. For them, the last straw was the aftermath of the Great Recession – from 2009, the country has recovered from the worst economic disaster since the Great Depression, but most of its people have not – in 2014, real median household income remained almost $4000 below the pre-recession level, and well below the level in 1999.

Of Trump's noisy arrival on the political stage, Frum writes: "Something has changed in American politics since the Great Recession. The old slogans ring hollow. The insurgent candidates are less absurd, the orthodox candidates more vulnerable. The GOP donor elite planned a [Bush] dynastic restoration in 2016. Instead, it triggered an internal class war." What to do as a fractured party stares defeat in the face? Frum sees four options: 1. Double down: The GOP elite concludes its failure was in not getting the right candidate up, and it sticks with its policy swag and goes in search of Mr or Ms Right Candidate – "yet even if the Republican donor elite can keep control of the party while doubling down, it's doubtful that the tactic can ultimately win presidential elections." 2. Tactical concession: Minimal concessions to the disgruntled to tighten immigration, as evinced by Cruz and New Jersey Governor Chris Christie in the primaries – "Yet a narrow focus on immigration populism alone seems insufficient to raise Republican hopes. Trump shrewdly joins his immigration populism to trade populism."

3. True reform: Party elites could try to open more ideological space for the economic interests of the middle class. Make peace with universal health insurance coverage; Mend Obamacare rather than end it. Cut taxes less at the top, and use the money to deliver more benefits to working families in the middle. Devise immigration policy to support wages, not undercut them. Worry more about regulations that artificially transfer wealth upward, and less about regulations that constrain financial speculation. "Take seriously issues such as the length of commutes, nursing-home costs, and the anti-competitive practices that inflate college tuition. Remember that Republican voters care more about aligning government with their values of work and family than they care about cutting the size of government as an end in itself." 4. Change the rules of the game: Let the Democrats have the presidency, and instead of being on offence, go on defence in Congress and in the state legislatures, where the party is supremely successful – "maybe the more natural condition of conservative parties is permanent defence – and where better to wage a long, grinding defensive campaign than in Congress and the statehouses? Maybe the presidency itself should be regarded as one of those things that is good to have but not a must-have, especially if obtaining it requires uncomfortable change." Frum concludes by wondering what the party is made of these days – how do the elites respond to retreat by their followers, is it capable of self-examination, does it hunker as it is or can it meet the challenge to somehow build a new political majority? Or does it just repeat its dogmas louder? The apocalypse may well be nigh. Some have taken to describing the party as a circular firing squad and in April 2016, George W. Bush was overheard telling attendees at a reunion of his administration staff of his worry that he was the "last Republican president".

Signing off in his letter from London, Garrison Keillor laments that Trump might have applied himself more usefully: "It would have been better if, instead of running for president and wasting everyone's time, he'd just sat down and written a novel." Again Keillor misses the point. Trump has written a spectacular novel on the self-immolation of a once revered political party – all that's left is to get it down on paper and into the bookstores.