Republicans were in trouble. Mitt Romney, their US presidential nominee, had been crushed by Barack Obama. The party commissioned an “autopsy” report that proposed a radical rethink. “If we want ethnic minority voters to support Republicans,” it said, “we have to engage them and show our sincerity.”

Ten years after Romney’s loss, Republicans are fighting their first election since the presidency of Donald Trump. But far from entering next month’s midterms as the party of tolerance, diversity and sincerity, critics say, they have shown itself to be unapologetically the party of hate.

Perhaps nothing captures the charge more eloquently than a three-word post that appeared on the official Twitter account for Republicans on the House of Representatives’ judiciary committee – ranking member Jim Jordan – on 6 October. It said, simply and strangely: “Kanye. Elon. Trump.”

The first of this unholy trinity referred to Ye, the rapper formerly known as Kanye West, who has recently drawn fierce criticism for wearing a “White Lives Matter” T-shirt at Paris fashion week and for antisemitic messages on social media, including one that said he would soon go “death con 3 on JEWISH PEOPLE”.

The second was billionaire Elon Musk, who published a pro-Russian peace plan for Ukraine and denied reports that he had been spoken to Russian autocrat Vladimir Putin.

The third was former president Donald Trump, who wrote last weekend that American Jews have offered insufficient praise of his policies toward Israel, warning that they need to “get their act together” before “it is too late!” The comment played into the antisemitic prejudice that American Jews have dual loyalties to the US and Israel.

It was condemned by the White House as “insulting” and “antisemitic”. But when historian Michael Beschloss tweeted: “Do any Republican Party leaders have any comment at all on Trump’s admonition to American Jews?”, the silence was deafening.

Republicans have long been accused of coded bigotry and nodding and winking to their base. There was an assumption of rules of political etiquette and taboos that could not be broken. Now, it seems, politics has entered a post-shame era where anything goes.

Jared Holt, an extremism researcher at the Institute for Strategic Dialogue thinktank, said: “The type of things they would say in closed rooms full of donors they’re just saying out in the open now. It’s a cliche but I always remember what I heard growing up which is, when people tell you who they are, you should believe them.”

The examples are becoming increasingly difficult to downplay or ignore. Earlier this month Tommy Tuberville, a Republican senator for Alabama, told an election rally in Nevada that Democrats support reparations for the descendants of enslaved people because “they think the people that do the crime are owed that”. The remark was widely condemned for stereotyping African Americans as people committing crimes.

And Marjorie Taylor Greene, a congresswoman from Georgia, echoed the rightwing “great replacement” theory when she told a rally in Arizona: “Joe Biden’s 5 million illegal aliens are on the verge of replacing you, replacing your jobs and replacing your kids in school and, coming from all over the world, they’re also replacing your culture.”

Such comments have handed ammunition to Democrats as they battle to preserve wafer thin majorities in the House and Senate. Although the party is facing electoral headwinds from inflation, crime and border security, it has plenty of evidence that Trump remains dominant among Republicans – a huge motivator for Democratic turnout.

Indeed, Trump did more than anyone to turn the 2013 autopsy on its head. In his first run for president, he referred to Mexicans as criminals, drug dealers and rapists and pledged to build a border wall and impose a Muslim ban. Opponents suggest that he liberated Republicans to say the unsayable, rail against so-called political correctness and give supporters the thrill of transgression.

Antjuan Seawright, a senior adviser to the Democratic Congressional Campaign Committee, said: “He has been the creator of the permission slip and the validator of the permission slip. For many of them, he is their trampoline to jump even further with their right wing red meat racial rhetoric.”

Beyond Republicans’ headline-grabbing stars, the trend is also manifest at the grassroots. In schools, the party has launched a sweeping assault on what teachers can say or teach about race, gender identity, LGBTQ+ issues and American history. An analysis by the Washington Post newspaper found that 25 states have passed 64 laws reshaping what students can learn and do at school over the past three academic years.

There are examples of the new extremism all over the country. The New York Republican Club will on Monday host an event with Katie Hopkins, a British far-right political commentator who has compared migrants to cockroaches and was repeatedly retweeted by Trump before both were banned by the social media platform.

In Idaho, long a deeply conservative state, Dorothy Moon, the new chairwoman of the state Republican party, is accused of close associations with militia groups and white nationalists. Last month she appeared on Trump ally Steve Bannon’s War Room podcast to accuse the state’s Pride festival and parade of sexualising children.

A recent headline in the Idaho Capital Sun newspaper stated: “Hate makes a comeback in Idaho, this time with political support.”

Michelle Vincent, a senior adviser to Democratic gubernatorial candidate Stephen Heidt, noted the such currents have long been a problem in Idaho but said: “Trump made hate OK. He made bad behavior seem OK because of the extremes of what he was doing. They started emulating him. People were were abused here during Black Lives Matter protests. We have so much militia here and they are out of control.”

In many cases, the naked bigotry goes hand in hand with Trump’s “big lie” that the last election was stolen from him due to widespread voter fraud. A New York Times investigation found that about 70% of Republican midterm candidates running for Congress in next month’s midterm elections have either questioned or flat-out denied the results of the 2020 election.

They can now count on support from Tulsi Gabbard, a former Democratic congresswoman and presidential candidate who in 2017 met with Syrian dictator Bashar al-Assad and dismissed his entire opposition as “terrorists” Gabbard this week defected to the Republicans and campaigned for Kari Lake, the Republican nominee for governor of Arizona and an unabashed defender of the big lie.

Another election denier is Doug Mastriano, a political novice running for governor of Pennsylvania with the help of far-right figures. He was outside the US Capitol during the January 6 insurrection and photographed watching demonstrators attacking police before he supposedly walked away.

Mastriano has repeatedly criticised his opponent, attorney general Josh Shapiro, for attending and sending his children to what he brands a “privileged, exclusive, elite” school, suggesting that this demonstrates Shapiro’s “disdain for people like us”. It is a Jewish day school where students receive both secular and religious instruction.

After a long courtship, Trump himself has in recent months begun embracing the antisemitic conspiracy theory QAnon in earnest. In September, using his Truth Social platform, the former president reposted an image of himself wearing a Q lapel pin overlaid with the words “The Storm is Coming”. A QAnon song has been played at the end of several his campaign rallies.

Ron Klein, chair of the Jewish Democratic Council of America, said: “It’s very unfortunate that the Republican party is either silent and complicit in this antisemitic language that’s being put forward by Donald Trump and others that align with him. But it’s very indicative of a Republican party that does not want to take on rightwing extremists.”

Klein, a former congressman, added: “Some members of Republican party did use dog whistles and symbolic language to make their points about minorities, including the Jewish community, and that was very troubling. But the era of Donald Trump has just lifted the rock under which these people now feel it’s OK and even helpful for them to make these kinds of statements and use these kinds of words to gain political power and political stature, which is very troubling in our American political system.”

The 2013 autopsy now looks like a blip, an outlier, in half a century of Republican politics. Richard Nixon’s 1968 “law and order” message stoked racial fear and resentment in the south. Ronald Reagan demonised “welfare queens” in 1976 and, four years later, launched his election campaign with a speech lauding “states’ rights” near the site of the “Mississippi Burning” murders – seen by many as a nod to southern states that resented the federal government enforcing civil rights.

A political action committee linked to George HW Bush’s campaign in 1988 paid for an attack advert blaming Democratic rival Michael Dukakis for the case of Willie Horton, an African American convict who committed rape during a furlough from prison. Lee Atwater, Bush’s campaign manager, bragged that he would turn Horton into “Dukakis’s running mate”.

The Atwater playbook is being deployed again in Senate midterm races as Republicans Ron Johnson of Wisconsin and Mehmet Oz of Pennsylvania run attack ads accusing their Democratic opponents, Mandela Barnes and John Fetterman, of being soft on crime, often with images of Black prison inmates.

Stuart Stevens, a veteran Republican campaign strategist who wrote a withering indictment of the party’s trajectory, It Was All a Lie: How the Republican Party Became Donald Trump, said: “I don’t think Donald Trump made people more racist or antisemitic; I think he gave them permission to express it.”

Stevens, a senior adviser at the Lincoln Project, an anti-Trump group, continued: “It’s a party of white grievance and anger and hate is an element of that.”

Kurt Bardella, a Democratic strategist and former Republican congressional aide, agreed: “The real consequence of Donald Trump’s presidency is it did give permission to so many people within the party who used to try to mask or hide their racism. They now feel like they can proudly wear it and they do.”

With hate crimes on the rise across America, there are fears that comments by Trump, Tuberville, Greene and others will lead to threats and violence that put lives in danger. Bardella added: “We learned after January 6 that, to the Republican party faithful, these aren’t just words, they are instructions. It’s a very dangerous development that one of the major political parties in America has made the conscious decision to wrap itself in the embrace of white nationalism.”