WASHINGTON — Joe Biden’s pledge in Thursday’s debate to “transition away from the oil industry’’ to address climate change put the issue on center stage for the final stretch of a campaign year in which the warming planet has played a larger role than ever before.

Biden’s statement in the closing moments of the debate gave President Trump what his campaign saw as an enormous opportunity to blunt his opponent’s appeal to working-class voters. Biden’s campaign tried to downplay it, saying he was merely stating that he would phase out longstanding tax subsidies.

But transitioning away from fossil fuels is the inevitable outgrowth of Biden’s promise to end net carbon pollution by 2050. That policy has energized some young voters and helped unite the Democrats’ left and moderate wings, but has always carried risks for Biden.

Hours after the debate, the campaign released a statement declaring that he would phase out taxpayer subsidies for fossil fuel companies, but not the industry altogether. Biden also dispatched running mate Kamala Harris to help clarify his position as she campaigned in swing state Georgia.

“Let’s be really clear about this: Joe Biden is not going to ban fracking,’’ Harris said, referring to a technique used to extract oil and gas. “He is going to deal with the oil subsidies. You know, the president likes to take everything out of context. But let’s be clear, what Joe was talking about was banning subsidies, but he will not ban fracking in America.’’

While ending the nation’s reliance on fossil fuel is popular among many liberals, the idea could hurt Biden among working-class voters in swing states such as Pennsylvania, Ohio, and Texas who depend on the industry, and fracking in particular, to make a living.

Trump’s allies immediately began running new attack ads seizing on the Democrats’ inconsistent answers on energy. One ad unveiled Friday calls Biden and Harris “fracking liars.’’ Another claims Biden’s plans could cost up to 600,000 jobs in Pennsylvania alone.

Trump returned to the point Friday as he campaigned at The Villages retirement home in Florida. “I said whoa, do you want to get rid of oil and gas?’’ the president said. “Is that — yeah, we want to phase it out. I said thank you, Texas, are you watching? Pennsylvania, Oklahoma, Ohio, are you watching?’’

Meanwhile, Biden gave a speech in Delaware in which he did not address oil policy, but instead stuck to his criticism of Trump for his handling of the pandemic, which polls suggest has turned many Americans against the president.

’’President Trump said he found a cure,’’ Biden said, drawing on the president’s remarks from the night before. “But let me tell you, we have 1,000 people dying every day.’’

In no political year has climate change been as dominant an issue as 2020.

Both presidential debates this year delved into the matter in depth for the first time. Biden campaigned hard on promises to reduce planet-warming emissions, and Trump even worked sporadically to moderate his longtime climate change denial by promoting tree-planting as an environmental solution.

Trump’s warning that Biden would endanger jobs in Pennsylvania and other oil and gas producing states was reminiscent of the Republican strategy in 2016. That year, Hillary Clinton acknowledged that “we’re going to put a lot of coal miners and coal companies out of business’’ as the nation moves to clean energy. Those comments resonated in coal states like West Virginia, Pennsylvania, Ohio, and Wyoming.

Biden’s comments may have put a new set of states in play that have looked friendly to Biden, like Texas and New Mexico. Representative Xochitl Torres Small, an endangered freshman Democrat in New Mexico, said on Twitter, “We need to work together to promote responsible energy production and stop climate change, not demonize a single industry.’’

Though more alluded to than stated outright, transitioning from fossil fuels will be necessary to meet Biden’s goals of eliminating emissions from the power sector by 2035 and reaching net-zero emissions across the economy by midcentury.

Yet he has walked a fine line throughout the campaign, insisting that natural gas production — and the jobs it creates — will remain a core part of US energy composition for several years to come even as he envisions a future powered more by wind, solar, and other renewable sources.

Some energy experts said the Trump campaign’s attacks on Biden may not have the same resonance as those on Clinton four years ago, in large part because public understanding of climate change has grown and the major oil companies of the world have, to varying degrees, pledged to reduce their emissions.

“This is a playbook that they keep coming back to, and it’s less and less effective. The economy is moving on, and the public is moving on,’’ said Joshua Freed, who leads the climate and energy program at Third Way, a center-left think tank.

“When you have the worst wildfires in history on the West Coast, when you have flood after flood after record-breaking storm and hurricane across the rest of the country, you have people saying, ‘This is a big problem and we want to see it addressed,’’’ he said.

During the debate, Biden and Trump engaged in a sustained debate about the economic effects of both addressing and failing to address climate change. And for what many analysts said was the first time ever, the candidates were asked to talk about the consequences of pollution on communities of color who disproportionately live near industrial sites.

“Its presence in both debates underscores the difference and the magnitude in which this issue is thought of as a voting issue and not just a niche issue in a party primary,’’ said Robert Gibbs, a former White House press secretary under former president Barack Obama.

Obama made climate change a centerpiece of his second term. The science around the dangerous consequences of climate change has gotten stronger. And increasingly Americans are faced with the reality of record-setting weather extremes along with floods, hurricanes, and wildfires.

“Americans have a different consciousness about climate change than they did 12 years ago,’’ said Anthony Leiserowitz, director of the Yale Program on Climate Change Communication.

And for the first time, climate change polled as a top issue for Democrats during the primaries, which Leiserowitz called “hugely consequential.’’

Trump has disparaged climate science and installed people who do not agree with mainstream science about climate change in prominent positions at both the White House and environmental agencies. He has sought to roll back every federal regulation aimed at reducing greenhouse gas emissions, moved to make it easier for aging coal plants to keep operating, and promoted greater oil and gas production.

Pressed for his policy in the debate, Trump claimed he has “so many different programs’’ to address climate change but offered no solutions beyond an executive order he signed to support a World Economic Forum tree-planting initiative. He attacked renewable energy and said, falsely, that retrofitting buildings to make them energy efficient would eliminate windows.

Biden called climate change an “existential threat to humanity.’’ His plan calls for spending $2 trillion over four years to boost renewable energy.

Material from the Associated Press was used in this report.