A strike pitting a resurgent trade union against the US’s three biggest carmakers has exposed key differences in labour relations among Republicans – even while animating their assault on Joe Biden’s self-styled “Bidenomics” policies.

Led by Donald Trump, the former president and 2024 party frontrunner, Republican hopefuls have seized on the stoppage by 13,000 United Auto Workers (UAW) members at General Motors, Ford and Stellantis production facilities in Missouri, Michigan and Ohio to highlight rumbling economic discontent as a catalyst to recapturing the White House. The UAW is demanding a 40% pay raise, shorter hours and better pensions for its members – and is threatening to spread the strike to other plants if its terms are not met.

Republicans – who have attacked unions for decades – believe they stand to gain from a dispute that could seriously test Biden’s claim to be the most pro-labour president in US history. Yet underlying their conviction is a divide between those professing sympathy for the strikers’ grievances and others who have invoked Ronald Reagan and Margaret Thatcher to suggest that they deserve to be sacked.

For his part, Biden has clearly sided with the union’s demands and urged management to share more of their companies’ record profits with the workforce.

Bullishly heading the Republican charge is Trump, who has made clear his intention to woo UAW members by scheduling a keynote speech in Detroit next week – the symbolic heartland of the US motor industry and near the site of the strike-hit Ford plant in Dearborn.

He will address 500 workers and union members from a range of industries – including carworkers – in a bid to reclaim the level of working-class support that enabled him to carry Michigan in his 2016 presidential victory over Hillary Clinton, before losing the state in his 2020 defeat to Biden.

Next Tuesday’s event will be timed to coincide with the second Republican primary debate in California, which he is deliberately skipping to shield his presumed status as the party’s anointed nominee-in-waiting.

“There’s something in this strike for Trump, and maybe one or two of the other Republicans,” said Larry Sabato, the director of the centre for politics at the University of Virginia. “It’s a political opportunity for Trump and he recognises it. Whatever you think of Trump, his political instincts aren’t bad.

“He needs something in the neighbourhood of 37% to 40% of union voters to win back Michigan, so he will come in and give a speech promising that he is their best, best friend and will be to their dying day – even though they will live longer than he will.

“He did pretty well in 2016 in Michigan, Pennsylvania and Wisconsin, partly because a lot of union members didn’t like Hillary Clinton but also because Trump’s swagger really seemed to appeal to many union members – they were attracted to that style of leadership.”

Shawn Fain, the UAW’s president, rebuffed Trump’s ostensibly union-friendly posture, saying in an issued statement: “Every fibre of our union is being poured into fighting the billionaire class and an economy that enriches people like Donald Trump at the expense of workers.”

Crucially, however, the UAW has yet to endorse Biden’s re-election bid, despite the president’s labour-friendly posture and his vocal support for the union’s demands – giving Republicans leeway to make inroads with its members.

Trump is not alone among the GOP field in displaying sympathy for the UAW – or at least its grassroots membership.

Describing himself as “among the most pro-labour Republicans in the US senate”, JD Vance, the senator from Ohio – a traditionally union-friendly state – said American carworkers had “gotten the short end of the stick” and declared: “I support the UAW’s demand for higher wages.”

But he qualified his support with an attack on the Biden administration’s “premature transition to electric vehicles”, calling it a “6,000lb elephant in the room”.

Vivek Ramaswamy, the rightwing populist presidential candidate and biotechnology entrepreneur, avoided choosing a side and said the union should direct its anger at the White House. “I empathise with workers who have seen wages not go up nearly at the same rate as prices have gone up,” he said. “The people they should be really protesting against is the current administration that has given us the economic policies of inflation without wage growth to go along with it.”

Contrasting with efforts to curry favour with the strikers are the hardline attitudes expressed by Tim Scott and Nikki Haley.

Scott, a senator for South Carolina, cited Ronald Reagan’s firing of striking air traffic controllers in 1981 as a model.

“I think Ronald Reagan gave us a great example when federal employees decided they were going to strike,” Scott said at a campaign event in Iowa. “He said, ‘You strike, you’re fired.’ Simple concept to me, to the extent that we can use that once again.”

In separate remarks, he accused the UAW of fighting for “more pay and fewer days on the job. It’s a disconnect from work.”

Analysts said Scott’s comments were motivated by a track record of known anti-union sentiment – illustrated by his sponsorship of a recent bill in the senate that critics say would curtail workers’ rights and a desire to attract business funds to finance his presidential campaign.

Haley, the US ambassador to the United Nations during Trump’s presidency who has repeatedly invoked Margaret Thatcher on the presidential campaign trail, appeared to identify with the former British prime minister’s famously uncompromising approach to striking trade unionists, boasting of being “a union buster” while governor of South Carolina.

“When you have the most pro-union president and he touts that he is emboldening the unions, this is what you get,” she told Fox News. “The union is asking for a 40% raise, the companies have come back with a 20% raise – I think any of the taxpayers would love to have a 20% raise and think that’s great.”

Samantha Sanders, the director of government affairs and advocacy at the Economic Policy Institute, a Washington-based thinktank, suggested Republican interventions on the strike were driven by opportunism.

“I don’t know what is the decision-making on their campaigns,” she said. “All I can say is, what is your track record? What have you done for workers? Have we reason to believe they would follow on these messages of support some of them express? I have not seen anything backed up by action while they were in office.