In a late gambit to win the battleground state of Pennsylvania, US President Donald Trump and his Republican allies have intensified attacks on Joe Biden over fracking.
Mr Trump hopes to drive a wedge between the former vice-president and the white, working class voters tied to the state’s booming natural gas industry.
That assault is playing out in a barrage of TV adverts and conservative and right-wing websites, and is repeated at every Trump rally in the state.
It relies on a series of confusing statements from the former vice-president – including remarks on the oil industry from last week’s debate – to claim he intends to “ban” or end national gas extraction, although that is not the Democrats’ official position.
Mr Trump’s fracking play comes as polls show the president is struggling to overtake Mr Biden in Pennsylvania and in need of a boost from the voters who helped him to a narrow victory in Pennsylvania in 2016.
It also shoots to snap the tightrope that Mr Biden is walking between the Democratic Party’s left wing, which is hostile to fossil fuels, and its bedrock blue-collar union base that is building an expanding network of gas pipelines, power plants and processing facilities in Pennsylvania.
Mr Biden’s climate change plan aims to reach net-zero greenhouse gases emissions by 2050 and does not involve banning fracking.
He argues net-zero threshold can be achieved by helping eliminate emissions from natural gas infrastructure, while redirecting government subsidies for oil and gas to cleaner energies.
“I do rule out banning fracking because … we need other industries to transition to get to ultimately a complete zero-emissions,” Mr Biden said in Thursday night’s debate.
For his part, Mr Trump often ridicules the science behind increasingly urgent warnings for immediate action to stave off the worst of climate damage by cutting fossil fuel emissions.
But Mr Trump’s attacks routinely cite various Biden statements – several made during the Democratic primary campaign – to muddy that position.
In one, Mr Biden told a town hall questioner last year: “We’re going to end fossil fuel.”
Mr Biden’s running mate, California Senator Kamala Harris, meanwhile endorsed a ban during her own bid for the Democratic presidential nomination.
At a recent Mr Trump’s rally in Erie, Pennsylvania, the president showed the crowd a video of various comments by Mr Biden on fracking in a bid to portray him as opposed to the process.
That was days before the pair tussled over energy during the debate.
After Mr Biden noted he wanted to “transition away from the oil industry”, Mr Trump pounced.
“Basically what he is saying is, he is going to destroy the oil industry,” Mr Trump said.
“Will you remember that, Texas? Will you remember that, Pennsylvania? Oklahoma? Ohio?”
Mr Trump will return to campaign in Pennsylvania on Monday.
While Mr Biden insists he does not want to ban fracking broadly, he does want to stop issuing new drilling permits on government lands, which its agencies say accounts for about 10% of natural gas production and 7% of oil production.
As part of a two trillion dollar plan (£1.5 trillion), he also wants to make electricity production free of fossil fuel emissions by 2035 and reach net-zero carbon emissions in the US by 2050 through technologies such as carbon capture sequestration.
Scientists say it is possible to achieve net-zero carbon emissions in the US by 2050 without eliminating the use of fossil fuels.
But Mr Biden’s nearer-term goal of eliminating emissions from power plants is sending a shiver through Pennsylvania’s industry because a growing fleet of natural gas-fired power plants is a big customer.
It is not clear how many votes are being decided by Mr Trump’s fracking claims in a contest where the vast majority of voters had already made up their minds.
But in a heavily populated and heavily contested state that Mr Trump won by just over 44,000 votes in 2016, any marginal change, no matter how slight, is significant, campaign strategists say.