The big picture: The trend to embrace more progressive energy and climate policies is part of the Democratic Party’s broader leftward shift over the last decade on various issues. (Republicans have moved to the right, but this column isn’t about them. This one is).

• The rise of the Green New Deal in the last eight months has accelerated and crystallized the Democratic Party’s leftward move. But that lofty proposal is an effect, not a cause of this shift, which has been underway for years.

Driving the news: Many of the Democratic presidential hopefuls support positions that were hardly emphasized in prior White House contests. Here are highlights, with much of the details courtesy of this Washington Post survey first published earlier this month.

• Banning fossil fuel development on public lands. This has been a talking point among some environmental activists for years, but it’s never permeated high-level politics like it has already in this contest.
• Supporting a price on carbon dioxide emissions. Hillary Clinton didn’t even include an explicit price on CO2 in her climate plan as the Democratic nominee in 2016. Yet today, not only are most candidates supporting one, it's not even enough by itself when they do to satisfy vocal and influential climate activists.
• Setting goals of reducing U.S. greenhouse gas emissions to zero. The aggressive benchmark had been something like an 80% reduction by 2050. Now it’s definitely zero emissions by then, if not by 2030. (Many experts say such goals would be very difficult to meet).
• Pledging not to take fossil-fuel campaign donations. Most candidates, including the front-runner Joe Biden, have pledged to sign the pledge. The pledge, run by several environmental groups including Oil Change U.S., has had a strong influence in just two years of existence.
• Banning fracking. This has become far more commonplace in today’s progressive debates than ever before. Clinton, who supported the controversial oil and gas extraction process as secretary of state under Barack Obama, came close to backing a ban at a 2016 primary debate against Sen. Bernie Sanders, who has long opposed fracking.

The intrigue: The drivers of these shifts are many and interwoven. Including…

• A stronger economy compared to the last few presidential contests.
• Increasing urgency from scientists about climate change.
• Growing concern for the environmental footprint of natural gas.
• Plummeting costs of renewable energy.

These factors, combined with Trump in the White House dismissing climate change, have supercharged activists successfully pushing Democratic politicians to adopt ever-more aggressive goals in the face of inaction at federal and global levels.

“Climate change is a unique public policy issue, in that it gets harder to solve the longer you wait. Since we haven’t taken adequate steps to solve the problem, the tools to solve the problem by definition have to become bigger, more aggressive and with shorter time frames.”

What I’m watching (beyond the debates this week): Whether the progressive climate positions espoused by most of the Democratic candidates are generally embraced by voters.

• As of January, climate change remains a low priority for Americans. It was second to last among a list of 20 priorities for Washington, according to a Pew Research survey from then.
• A recent CNN poll suggests Democratic primary voters are far more concerned about climate change than past elections, but it’s not yet clear how broad such support goes beyond that subset.
• There’s also what I’ve described as the big climate disconnect: More people around the world are saying they’re worried about climate change — but that concern is not translating into a willingness to pay more for energy or vote for candidates supporting aggressive action on the issue.

The bottom line: This presidential contest, both the Democrats’ primary fight and the general election, will be one of the clearest tests of people’s appetite to support aggressive climate policies.

Why you'll hear about this again: "Legal experts warned [the proposal] could cause further problems for the administration in court, where judges have suggested officials need to do a better job of assessing the climate impact of their decisions," per the Post.

Details: The guidance from the White House Council on Environmental Quality would cap the degree to which agencies have to calculate greenhouse gas emissions for projects unless "a sufficiently close causal relationship exists” with greater carbon emissions, the Post reports.

Go deeper: Trump’s UN pick breaks with White House on climate change

Reality check: America's coal industry continues to decline, driven by a host of factors separate from the Obama-era regulation, largely — but not only — because plentiful supplies of natural gas provide power companies a cheap, cleaner-burning alternative.

• Meanwhile, the CPP never actually went into effect, despite the hype from Obama administration officials and environmentalists. In an unusual move, the Supreme Court temporarily blocked the final rule in February 2016 to let litigation play out.

Details: The rule aims to reduce power-plant CO2 emissions by as much as 35% below 2005 levels in 2030, according to the EPA, which said this decline is also due to "expected industry trends," highlighting the ongoing shift away from coal to natural gas and renewable energy — irrespective of both Obama's rule and Trump's efforts to repeal it.

• Between the lines: The EPA's assessment is an implicit acknowledgement that its new rule isn’t going to bring back coal.
• America's greenhouse gas emissions, like much of the rest of the world's, ebb and flow with economic growth and demand. After a marked decline due to the shift from coal to natural gas, which burns far less CO2 than coal, U.S. energy-related emissions are expected to decline again slightly in the coming years.

The intrigue: Myron Ebell, a top director at the Competitive Enterprise Institute, a conservative think tank that disputes that climate change is a problem, said Wednesday that his group will likely sue EPA over the rule, arguing the law doesn’t allow such regulation on CO2.

• Ebell, who was an adviser to the Trump transition team, said this would be the first lawsuit his group would file against Trump’s EPA, which has been mostly pushing policies Ebell supports.

What's next: Expect lawsuits from environmental groups and Democratic-led states. In other deregulatory news, EPA's other big controversial rollback — freezing Obama's auto efficiency standards — is expected soon.

Go deeper: The U.S. coal industry is choking