Dive Brief:

Emails stolen from Hillary Clinton's campaign chair and released by WikiLeaks reveal the candidate was previously more supportive of natural gas production and infrastructure, privately criticized climate activists and resisted pressure to endorse a carbon tax earlier in the campaign.

Under pressure by supporters of nomination rival Sen. Bernie Sanders (I-VT), emails sent to and from campaign chair John Podesta show the Clinton team rejected a carbon tax due to poor internal polling and attempted to frame its support of natural gas fracking as a bridge to a cleaner power system.

Other emails reveal the Clinton team considering permanent extension of tax credits for wind and solar energy, and Podesta's support for a "close to zero carbon energy sector" by 2030. Even so, the campaign manager has been rushing to reassure activists of Clinton's commitment to environmental protection.

Dive Insight:

While energy policy has been scant on the campaign trail in recent weeks, leaked emails purport to show that the campaign of Bernie Sanders, who opposes hydraulic fracturing and supports a carbon tax, made things uncomfortable for Clinton behind the scenes.

In one email, a transcript of a speech to the North America's Building Trades Unions in the fall of 2015, Clinton said "my view is I want to defend natural gas. I want to defend repairing and building the pipelines we need to fuel our economy. I want to defend fracking under the right circumstances."

In the same speech, Clinton mocked environmental activists who have pushed her to commit to curtailing fossil fuel production.

"They come to my rallies and they yell at me and, you know, all the rest of it," Clinton said. "They say, 'Will you promise never to take any fossil fuels out of the earth ever again?' No. I won't promise that. Get a life, you know."

Ultimately, the campaign shifted toward more restrictive rhetoric on fracking and an emphasis on green energy, a move illustrated in other campaign emails.

"I would watch our tone and not sound too pro-fracking," Colorado campaign manager Bradley Komar said in one email. "A reluctant tone is a better fit for Dem caucus goers (it's a transition energy. It's not great but it allows us to get to where we want to be)."

A separate email chain shows the Clinton camp discussing how to frame a permanent extension of production tax credit (PTC) and investment tax credit (ITC) for wind and solar energy in an interview with National Journal reporter Ben Geman.

"[I]f Ben asks whether we would support a permanent extension of the PTC/ITC we need to hedge given out solar/renewable targets," Clinton advisor Melia Fisher wrote. "May need to call for 'extending and improving' or something like that."

Sanders's support for a carbon tax also sparked debate inside the Clinton camp, Vox noted. In January 2015, Podesta emailed a Clinton advisor saying he had seen "extensive polling" on a tax, and "it all sucks."

While some of Podesta's comments have roiled environmentalists, other emails show that the former White House chief of staff understands the urgency of climate change and the ambition implied in the Paris climate accord, which seeks to limit warming to 2°C this century.

“We need the get to 80% emission reduction by 2050,” Podesta wrote in an email to a Clinton staffer. "Which implies close to a zero carbon energy sector.”

The Clinton camp has largely refrained from commenting on specifics in the emails, with a number of outlets noting their authenticity has not been verified. But Podesta has been on something of an apology tour this week, and he told Grist that Clinton's policies "would exceed the goals that the United States took on in the Paris negotiations.”

Clinton is polling well ahead of Republican nominee Donald Trump in the final weeks of the election. Whoever wins will hold significant sway over the country's energy future, though market forces are moving towards cleaner sources independently. Whoever is elected will make appointments to key positions, determine how or if to defend climate commitments, and determine the government's level of clean energy procurement.