It seemed that Joe Biden would be bad for business in “Make America great again” world.

In theory, the US president, a white man with working-class roots and moderate policy positions, was a more elusive target for Donald Trump’s increasingly extreme support base than other prominent Democrats.

But after his first year in office, it transpires that Biden is not too boring to be a rightwing boogeyman after all.

“He’s our best salesperson,” said Ronald Solomon, a merchandiser who sells a $21.99 T-shirt depicting the president with an Adolf Hitler-style mustache and the slogan “Not My Dictator”. “Sales for Trump stuff and anti-Biden merchandise is the highest it’s been except for the three months leading up to the 2020 election.”

The demonization of Biden as a Hitler, Stalin or anti-white racist bears no relation to reality. But for many Republican voters it appears to stick, the product of relentless conservative media attacks, the president’s own missteps, and seething frustration during a seemingly never-ending pandemic.

At first Biden did excite less animus than Barack Obama, the first Black president who was subjected to conspiracy theories about his birthplace and the rise of the populist Tea Party movement. Biden never had to go through the misogyny endured by Hillary Clinton.

His policy record was also non-incendiary. When Trump supporters gathered at the annual Conservative Political Action Conference under the banner “America vs socialism”, the biggest hate figures were Senator Bernie Sanders, a democratic socialist from Vermont, and Congresswoman Alexandria Ocasio-Cortez, a liberal Latina from New York.

Since moving into the White House, however, Biden has granted Sanders a prominent voice in shaping his policy agenda. The unexpected scale of the president’s ambition to spend trillions of dollars on coronavirus relief, the social safety net and the climate crisis has fed into a Republican narrative that he is a puppet of the radical left.

And although Biden’s identity as a white man neutralised other “isms”, he cannot escape ageism. At 79, he is the oldest American president in history, his every verbal slip seized upon as cause to doubt his mental fitness. Last May, Fox News host Sean Hannity displayed a sippy cup with the presidential seal on it, floating the nickname “Sippy Cup Joe”.

In August, Tucker Carlson told viewers of the same network: “Maybe the most important thing we’ve learned is that Joe Biden is not capable of running the country. Joe Biden is senile.” (Such commentators rarely note that Mitch McConnell, Republican minority leader in the Senate, is also 79.)

Another popular line of attack is to compare Biden to Jimmy Carter, whose presidency in the 1970s ended in failure after one term. “Joe Biden Is Jimmy Carter 2.0,” said one such press release from the Republican National Committee. “On Joe Biden’s watch, America is grappling with a gas crisis, record-breaking inflation, weak leadership abroad, and Americans trapped behind enemy lines, all reminiscent of the Jimmy Carter years.”

But there is no greater symbol of anti-Biden sentiment than “Let’s go Brandon”, a phrase that originated at a Nascar race in Alabama in October. Brandon Brown, a 28-year-old driver, had won his first Xfinity Series and was being interviewed by an NBC Sports reporter.

The crowd behind him was chanting something that at first was hard to hear. The reporter suggested they were saying “Let’s go, Brandon!” to support the driver. But it became increasingly clear they were chanting, “Fuck Joe Biden!” So it was that “Let’s go, Brandon” became conservative code for insulting the president and went viral.

On a Southwest flight from Houston to Albuquerque, the pilot signed off his greeting over the public address system with the phrase, leaving some passengers aghast. On Christmas Eve, when Biden fielded a few phone calls to the Norad Santa Tracker, Jared Schmeck, a Trump supporter from Oregon, said: “Merry Christmas and let’s go, Brandon!”

Speaking from Las Vegas, Solomon, president of the Maga Mall, said he has a line of “Let’s go, Brandon” merchandise including banners, buttons, T-shirts for men and women and hats in four different colors. “One, it’s an attack on the mainstream media: this gal from NBC Sports immediately tried to make it like they were saying something that they weren’t,” he explained.

“Two, it’s a way for Republicans that don’t want to use a four-letter word to have a chance to say something that attacks the president of the United States, who they can’t stand any more.”

In a nod to the Trump base, Republican senator Ted Cruz posed with a “Let’s go, Brandon” sign at baseball’s World Series. McConnell’s press secretary retweeted a photo of the phrase on a construction sign in Virginia. Congressman Jeff Duncan of South Carolina wore a “Let’s go, Brandon” face mask at the US Capitol. Jim Lamon, a Senate candidate from Arizona, used the slogan a TV campaign ad.

Critics point out that goading, provoking and outraging their opponents, known as “owning the libs”, has become the defining principle of a Republican party that lacks a coherent ideology of its own. McConnell reportedly told donors last month that he would not be putting forward a legislative agenda for November’s midterm elections because he was content to merely hammer away at Democrats.

But with Biden’s approval rating hovering in the low 40s, and his Build Back Better agenda stalled in Congress, the Republican formula might be working.

John Zogby, a pollster and author, said: “They have made significant inroads into demonizing him. In the beginning, of course, it was hard. He was a softer target, he was Uncle Joe, he had a high favorability rating and he’d been around a long time.

“But definitely in the second half of this first year, the almost-mantras of the Republican party have gained hold: he’s too old, he’s a socialist, and then this whole ‘Let’s go, Brandon’ thing. Plus the fact that they’ve been able to successfully block the bigger initiatives so not only a socialist, but a socialist who can’t succeed, is the message.”

Barbs and brickbats aimed at a Democratic president are hardly new. Before Obama there was Bill Clinton, who drew his share of rancor, vitriol and baseless conspiracy theories. In today’s hyper-polarized Washington, inflamed by social media, the incumbent can expect to have everything but the kitchen sink thrown at them.

Allan Lichtman, a distinguished history professor at American University in Washington, said: “As long as you have the capital D as your political designation, you are a target for the Republicans. It doesn’t matter if you are a leftwing or moderate Democrat – it makes absolutely no difference.

“Bill Clinton was a centrist. He was the head of the Democratic Leadership Council, dedicated to moving the Democrats to the centre, and yet they relentlessly attacked him, even impeached him. Republicans will oppose essentially anything that a Democratic president proposes and relentlessly attack them.”

Others argue that Biden has done Republicans’ work for them with a botched Afghanistan withdrawal, a crisis at the southern border, the highest inflation for 40 years and an inability to curb the pandemic. The president’s newly aggressive stance on voting rights and safeguarding democracy has also rallied Republicans against him.

Frank Luntz, a Republican pollster and strategist, said: “Incredibly, Joe Biden has a worse approval rating at this point than Donald Trump did and it’s not because of Republican critiques. It’s because of Biden’s failures.

“He’s failed to communicate effectively. He’s failed to try to bridge the gap; in fact, he’s been promoting greater division. He’s promised too much on Covid and hasn’t delivered. And nothing bothers people more than rising prices because that affects everyone, whether you are working class, middle class or somewhat affluent.”