Democrats who want to tackle climate change are about to face the biggest challenge with sweeping policies: They're much more likely to pass if they get support from both sides of the political aisle.

Why it matters: No matter how far-fetched it seems after the government shutdown, the fact remains that policy endures better with bipartisan support, political scientists and past precedent suggest. This is particularly relevant in trying to solve a problem as enormous as climate change and with progressive Democrats rallying around a Green New Deal that calls for massive economic transformation.

“While the theory of having some collaboration and compromise across the board is always good, it’s particularly important when the progress is measured in decades. One of the unique challenges of the energy and climate debate is that no meaningful decision gets made unless people have some confidence in at least a decade of consistent policy.”

— Jason Grumet, president, Bipartisan Policy Center

Driving the news: After an absence of nearly a decade, two big climate and energy policies are emerging in the Washington debate. The Green New Deal represents the progressive flank of the Democratic Party, but it has no Republican support. The other, a carbon tax, is bipartisan and reflects controversial compromise.

By the numbers: While America’s political discourse has gotten more partisan in recent years, actual laws passed by Congress have not, according to forthcoming research described to Axios by James Curry, political scientist at the University of Utah, and Frances Lee, politics professor at the University of Maryland.

Since 1985, majority parties controlling Congress have passed just 12 laws getting largely what they wanted on big policy priorities over the opposition of most members of the minority party and the minority party's top leaders.

That’s less than 5% of all the majority-party policy priorities considered in more than 30 years.

Of the 12 that have passed by rolling the minority party, two have been high profile and more recent, making it perhaps seem more common when it actually isn’t: the Affordable Care Act of 2010, which Democrats pushed through with no GOP support, and the 2017 tax overhaul law, which got no Democratic votes.

Republicans, meanwhile, have been chipping away at the health care law since it passed, eroding its effectiveness.

Examples of bipartisan bills include two comprehensive energy bills in 2005 and 2007 and a 2015 spending bill that featured policies with big repercussions for energy and climate: lifting the 40-year-old ban on oil exports and extending wind and solar tax credits.

“It’s extraordinarily difficult to pass anything that’s partisan. It’s not happening more than it used to. It’s something that needs to be understood by activists.”

— Frances Lee, University of Maryland professor

Enter the Green New Deal, which features numerous lofty energy initiatives like a goal of 100% renewable electricity within 10 years (up from 17%), and other big non-energy policies, including a federal jobs guarantee and universal health care. More policy details are expected within the next week or so.

Dozens of congressional Democrats, including several presidential contenders, have expressed support for the idea. But no Republicans have, and even some more centrist Democrats have expressed concerns about it.

Backers of this proposal, including The Sunrise Movement, a youth-led group pushing the policy along with Democratic Rep. Alexandria Ocasio-Cortez, say the plan has to be done in one fell swoop, not piecemeal, given the urgency of climate change.

Meanwhile, a carbon tax where the proceeds go back to consumers in the form of a dividend check is gaining support in pockets across the political spectrum. Bipartisan legislation was just introduced in the House, while some oil companies are beginning to fund a similar effort.

To varying degrees, these proposals preempt other climate regulations, and in at least one instance provide a legal shield for oil companies facing certain kinds of lawsuits.

These two aspects, which are drawing ire from environmentalists, reflect what the backers say is essential compromise to get legislation passed.

Flashback: In 2009, when Democrats controlled both chambers of Congress and the White House, backers of comprehensive climate legislation failed to get support from enough Democrats, let alone any Republicans. It passed the House but died in the Senate. Most elected Republicans have ignored or dismissed climate change since then, but that’s slowly starting to change.

“Just look at how volatile, partisan and harsh the political environment in the legislative branch has become since the era of trying to do things with just one party,” said Rep. Francis Rooney of Florida, who is the only Republican co-sponsoring the carbon tax bill introduced last week.

What’s next: As bipartisanship inches back to life in some corners on Capitol Hill, don’t expect it to make a grand comeback until at least after 2020. Getting beyond partisanship is unlikely in what is shaping up to be a record-setting polarizing presidential election.