E-mails revealed by Wikileaks in an apparent attempt to embarrass Democratic presidential candidate Hillary Clinton may instead reveal her advisors’ policy instincts in the fight to restabilize the climate: a broad national carbon tax.

Two years ago, Clinton’s policy development team “floated a carbon tax in a planning document titled ‘Climate Change Framing Paper,’ released by WikiLeaks [last] week,” the Christian Science Monitor reports. The 19-page report called steps taken to that date by the Obama Administration “far from sufficient to meet the climate challenge.”  By the spring of 2015, some advisers were urging candidate Clinton to pursue a carbon price, “even suggesting a $42 per ton price for carbon emissions in a March 2015 memo,” the Monitor notes.

As the primary season in U.S. politics built up steam, however, “aversion to a carbon tax grew” among Clinton’s political advisors. In a June 2015 email, campaign manager Robby Mook called the idea “lethal”.

Virtually every climate economist supports the principle of placing a price on carbon, with many arguing that a tax—with rebates for lower-income groups—is the simplest, most effective mechanism to administer. Nonetheless, as the Monitor notes, “a carbon tax is unpopular with many conservatives, as they see it as extending government control and raising prices for gasoline and electricity.”

“Anybody who understands the politics of what [a carbon tax] will require in Washington, D.C., they understand it’s a fantasy and it will never happen,” former George W. Bush adviser and current financial lobbyist Dave Banks told the paper.

The Clinton campaign eventually came to the same conclusion, it appears, disappointing Brad Johnson, executive director of Climate Hawks Vote, for one. Clinton’s decision to campaign on a rejection of a carbon tax, Johnson said, reflected a “defeatism” among “too many progressives and climate activists” that can become self-fulfilling.

But other American climate activists were more resigned, the Monitor notes. “Short of a Democratic wave election, more Republicans must get on board with climate legislation to pursue a carbon tax, anyway,” the outlet writes, citing David Goldston, director of government affairs with the Natural Resources Defense Council.

“Clinton has been clear that she’s committed to climate action,” Goldston told the outlet, “including meeting the Paris goals, which will require building on the Obama Administration’s actions.”

Without a carbon tax, however, that task “would be like attempting to climb a very steep mountain with one leg tied behind your back,” Jessica Tuchman Mathews, a past-president of the Carnegie Endowment for International Peace, warned earlier this year.

The strength and composition of any potential Clinton victory are likely to influence whether her advisors consider revisiting a carbon tax any less lethal after November 8.