Now that what once seemed inconceivable has happened, what are Americans who care about their country, its hard-won values and its leading international role going to do about it? The prospect that Donald Trump will secure the Republican party’s presidential nomination at its Cleveland convention in July can no longer sensibly be ignored or denied. Revised delegate counts last week indicated the property tycoon commands a majority going into the first ballot. It appears only an unprecedented internal party coup, or some kind of personal meltdown or disqualifying scandal can stop Trump running for the White House in November as official GOP nominee.

That Trump cannot be considered a fit and proper person to occupy the office of president should be evident. But if the rumbustious primary season has demonstrated anything, it is that large numbers of voters are so angry about the state of their country, so dissatisfied with the system and so fearful of global changes that they seem ready to suspend normal, informed judgment. A vote for Trump is a vote against the status quo. But in too many cases, it is also an immature, isolationist, tantrum cry for a return to a mythical Fortress America that supposedly existed before Muslims and Mexicans and other “foreign” influences arrived on Main Street.

Faced with such negative electoral dynamics and unable to believe that Trump could succeed, Democrat leaders in Congress, moderate Republicans, and even Barack Obama have been too cautious about confronting him head-on. This is a mistake. The voters’ mood is not untypical. Every national election brings calls to “throw the bums out” but the feeling is particularly vitriolic this year. It has been exploited and manipulated by Trump, crassly and mendaciously regurgitating the simplistic, know-nothing prejudices and ignorant half-truths of a saloon-bar boor. As a result, until now, too many public figures have kept their heads down. Too frequently, his falsehoods and slanders pass unchallenged.

The next weeks and months will see a concerted, well-funded effort to render Trump respectable

Much of the US mainstream media seem unable or unwilling to get to grips with his candidacy. The sort of detailed scrutiny that has destroyed the ambitions of previous candidates seems lacking. Who remembers Gary Hart, whose presidential hopes sank without trace in 1988 when his reputation as a womaniser caught up with him on a yacht called Monkey Business – and the newspapers exposed all? Who does not recall the media pursuit of Bill Clinton, especially after the Monica Lewinsky affair came to light?

There are exceptions. The New York Times published an investigation into Trump’s misogynistic and abusive treatment of women employees and colleagues. But much of the coverage of his personal and business life, policy U-turns and self-contradictions, offensive and gauche remarks, and plain ignorance of the big issues facing the US and the world has been flaccid to the point of fawning. Even when the ugly truth is told, it somehow does not seem to damage him.

Fortunately for US democracy, there remain brave souls ready to stand up for their own and the country’s traditional values and beliefs, ready to run the gauntlet of Fox television “news”, the mockery of rightwing shock-jocks, and the merciless pillorying by anonymous social media nerds. Elizabeth Warren, a Democrat senator from Massachusetts, is one such. She does not suffer from undue diffidence. The woman Trump has crudely dubbed “Pocahontas” because of her Native American family background has been taking him on in a way that shames less courageous politicians.

“Let’s be honest – Donald Trump is a loser,” Warren said last week. “And Trump seems to know he’s a loser. His embarrassing insecurities are on parade: petty bullying, attacks on women, cheap racism and flagrant narcissism. But just because Trump is a loser everywhere else doesn’t mean he’ll lose this election. People have been underestimating his campaign for nearly a year – and it’s time to wake up.

“Consider what hangs in the balance. Affordable college. Accountability for Wall Street. Healthcare for millions of Americans. The supreme court. Big corporations and billionaires paying their fair share of taxes… The chance to turn our back on the ugliness of hatred, sexism, racism and xenophobia. The chance to be a better people… Many of history’s worst authoritarians started out as losers – and Trump is a serious threat. The way I see it, it’s our job to make sure he ends this campaign every bit the loser that he started it.”

Warren’s impassioned call for America’s voters to stand up for what they believe, or in the case of Trump’s supporters, come to their senses, was long overdue. And it badly needed saying. Trump and his pernicious brand of divisive, bombastic and racialist politics will not be defeated by wishful thinking. It is going to be a long, hard fight. The next weeks and months will see a concerted, well-funded effort to render Trump respectable. Already, for example, his spokespeople claim his call to ban Muslims from the US was merely a “talking point”. Already, the ever pragmatical Foreign Office is advising that the special relationship must come first. Already, David Cameron is mending fences, congratulating Trump on his success and inviting him to Downing Street.

A line must be drawn. Illusions must be discarded. The truth must be told. Trump, with his innate, rich man’s hostility to social justice and equal rights, with his greedy love of big business and corporate tax cuts, with his scornful disdain for green policies and climate change science, with his alarming ignorance of strategic realities in the Middle East and east Asia, with his cruel and ruthless contempt for the weak, the less privileged and the vulnerable of this world, with his foolhardy isolationism and protectionism, with his loathsome self-adoration, and with his hateful fear-peddling is a menacing problem, not a passing phenomenon.

Something not dissimilar to the rise of Trump is happening across Europe, where xenophobic and racist parties of the right are advancing, most recently in Austria last week. Trump-ism, for want of a better word, is not something with which tidy, reasonable compromises can be made. It must not be appeased, bought off or left to fester. The only thing to do with Trump-ism, wherever it appears, is to oppose it, fight it, and defeat it. As Elizabeth Warren says, that critical fight must start now.