Joe biden was quick to pounce after donald trump urged his fans to boycott goodyear, the ohio-based tire company, because it had banned staff from wearing clothing with political slogans such as make america great again.

Mr biden ran an ad accusing mr trump of abandoning the working-class voters who helped him win ohio and the white house in 2016, claiming the president would risk american jobs to try to save his own.

The democratic challenger is expected to make the same argument on tuesday, when the candidates take part in the first presidential debate in ohio, a bellwether state that no republican has lost without also losing the white house.

Four years ago, mr trump beat hillary clinton by eight points in ohio, thanks to support from white, working class voters angered by trade deals that sent factory jobs to china. many political experts subsequently concluded that ohio had turned solidly republican.

But with five weeks until the election, mr biden has a lead of 3.3 points in ohio, according to the real clear politics polling average.

Early in 2020, before the pandemic, everyone had put ohio in the safe column for trump...but now the world has turned upside down, said lauren copeland, a politics professor at baldwin wallace university in cleveland.

Line chart of ohio manufacturing jobs, not seasonally adjusted, thousands showing ohio steadily gained jobs in manufacturing until coronavirus pandemic

Whether mr biden can win the state back has implications not just for ohio, but also nearby states such as wisconsin, pennsylvania and michigan, where he is trying to convince working-class voters to return to the democrats.

Kyle kondik, an expert on ohio politics at the university of virginia, said he thought mr trump would clinch the state, but added that a win for mr biden would likely mean a string of victories in the rust-belt and midwestern states that mrs clinton unexpectedly lost in 2016.

If biden were to win ohio, that would mean michigan and wisconsin were not that competitive, mr kondik added. theres no path for trump if he loses ohio.

Mr trump says he has brought jobs back to ohio. the number of manufacturing jobs rose 2.5 per cent over his first three years in office until the pandemic struck, but the rise was lower than the national average of 4.3 per cent. polls still show that the economy is one of the few areas where mr trump has an edge over mr biden in ohio.

Tim burga, head of the ohio branch of the afl-cio, the biggest us union organisation, said the state had been losing jobs for years, opening the door to mr trump in 2016. but he said that the president had failed to turn things round, citing ohios trade deficit, which has worsened since 2016, and the fact that china has become the biggest exporter to the state.

Donald trump talked a big game when he was here in 2016, but has a long list of broken promises, he added.

Mr burga is working to win over ohio workers who may still have an affinity for mr trump, including in the mahoning valley, an industrial area in eastern ohio that was a democratic stronghold for decades until mr trump won over the so-called trump democrats.

But some political experts said mr biden could struggle to win back disaffected working class voters. paul sracic, a politics professor at youngstown state university in mahoning valley, said mr trump seemed to have expanded his support in the area. it looks like a shrine to trump around here, he said, referring to the number of yard signs supporting the president.

Mr sracic noted that local workers had long been unhappy with nafta, the clinton-era trade deal that mr trump renegotiated into the us-mexico-canada trade agreement. nafta had a worse reputation than osama bin laden in this area, he added.

Democrats criticised mr trump after gm announced the closure of a plant in lordstown in 2018. but arno hill, lordstowns republican mayor, said the media had focused on the closure and did not pay enough attention to the fact that the carmaker was building an electric battery cell factory in the area.

Margin of victory in recent presidential elections

Mr biden has partly focused his television advertising on youngstown, which is near lordstown, but mr hill said he had not seen much evidence of a big push in the area.

Were the land of busted dreams and broken promises, mr hill said. the democrats have always taken this place for granted.

Mr sracic said the concern for mr trump was not so much areas such as mahoning, but rather the suburbs of cities where republican voters have started drifting away from the president despite supporting him in 2016.

Nan whaley, the democratic mayor of dayton, said many suburban women were turned off by mr trumps response to the anti-racism protests and that he had a growing problem with republican women because of his handling of the pandemic. a recent fox poll in ohio found that women favoured mr biden by a margin of 55-41 points.

One republican suburban woman last month told me... we all silently voted for trump and were now all silently voting for biden, said ms whaley.

Line chart showing ohio polls

Mr biden also appears to be doing better with black voters than mrs clinton did four years ago. father benjamin speare-hardy, the african-american rector of st margarets episcopal church in dayton, said he was doing a bit better.

But he warned that the campaign needed to be more active in winning support from black voters in dayton. there is a lot of work to be done [including] investing more dollars here, especially in african-american media, he said, adding that he had made this argument on calls with prominent black supporters of mr biden.

He is not the only one who wants to see more investment. while mr burga did not criticise the campaign, he said that with the polls tightening, significant investment in the state is going to pay dividends.

Ms whaley agreed: they should invest more in ohio. were doing that well and theyre not even investing.