If Joe Manchin gets what he wants in negotiations with the Biden White House and his fellow Democratic senators regarding climate policy, which now seems likely, it could have a devastating impact on the planet—and on Democrats’ prospects in 2022.

How so? Let’s answer that question by asking and answering two other questions.

First: Name an issue that young people—an increasingly important and frequently decisive voting bloc—are passionate about? When the US Conference of Mayors surveyed potential voters between the ages of 18 and 29 in 2020, 80 percent said the climate crisis was “a major threat to human life on earth as we know it.” By a 3-1 margin, young people said “bold measures” needed to be taken to address that threat.

Second: Name the issue that Democrats are now talking about downplaying in the ”Build Back Better” agenda in order to secure the West Virginia senator’s support? The Biden administration is by all accounts preparing to cut from the budget plan the Clean Electricity Performance Program (CEPP), a key climate initiative that would use a combination of incentives and mandates to get utilities to embrace renewable energy.

Much of the serious reporting on the issue has focused on the devastating impact that losing those clean-energy provisions could have on upcoming climate negotiations at the United Nations Climate Change Conference in Glasgow, Scotland. Without them, it will be tougher for Biden to convincingly pledge a 50 percent reduction in US carbon emissions by 2030. That could undermine negotiations on the issue, according to Michael Mann, director of the Earth System Science Center at Penn State. So serious is the threat that Mann greeted the news of Manchin’s push to abandon the CEPP by declaring, “Joe Manchin just launched a hand grenade at Glasgow.”

The president and House Speaker Nancy Pelosi say they will continue to focus on global warming concerns. But Representative Alexandria Ocasio-Cortez (D-N.Y.) is right when she argues that clear action to reduce emissions “is not something you can kick down the line.”

Young people know this. They understand the difference between “bold measures” on climate and mere hot air. Promises will not be sufficient to mobilize the mass turnout of these voters, who are far more likely to cast Democratic ballots than older voters, in 2022. Without that mass turnout, Democratic prospects will dim.

Democrats are already on shaky ground heading into next year’s elections. A so-called “midterm curse” often costs the party that holds the White House seats in Congress. With a 50-50 tie in the Senate, and with only a narrow majority in the House, Democrats can’t afford any losses. They have to beat the curse. To do so, however, they will need the support of young people, just as they did in 2018 and 2020.

“Half of Americans ages 18-29 cast a ballot in the 2020 general election, one of the highest youth voting rates in recent history and an 11-point increase from 2016 (from 39% to 50%),” according to the Center for Information & Research on Civic Learning and Engagement. That turnout increase provided a critical boost for Biden, as voters age 18–29 favored the Democrat by an overwhelming 60-36 margin over then-incumbent President Donald Trump. Among 18–24-year-olds, the margin jumped to 65-31 in the CNN exit poll.

The role that young voters played in the last midterm election was even more critical for the Democrats.

As Tom Bonier, CEO of the political data analysis group TargetSmart explained, the youth vote lagged more than that of any other group, accounting for only 7.2 percent of the votes: “The end result? Republicans won the national popular vote for the US House by almost 6 points, adding 13 seats to their already substantial majority. The GOP also gained 9 seats in the US Senate.”

“Jumping ahead to the 2018 midterm elections, no age group saw a larger surge in turnout than voters under the age of 30,” he added. “The youth vote drove the Blue Wave, as this group gave Democrats a margin of almost 2 to 1. In the end, voters under the age of 30 accounted for 11.4% of all votes cast, a 4.2-point increase over their 2014 vote share. Of course, 2018 saw Democrats recapture the House, winning the national popular vote by almost 9 points—a swing of almost 15 points from the previous midterm election.”

Democrats will need that level of support, or more, from young people in 2022. But it is far from assured that they will get it.

Polling conducted in the spring of this year by Hart Research Associates for the League of Conservation Voters found that young voters “want and expect action on climate, and absence of such action would substantially endanger Democratic candidates gaining their votes next year.”

At this point, according to a polling memo from Hart’s Geoff Garin, Jay Campbell, and Corrie Hunt, 44 percent of young voters are not certain they will vote in 2022. “However,” the memo adds, “79 percent of young Democrats say they would be MUCH more motivated to vote for Democrats in 2022 if Democrats take strong action on combating climate change to address the causes of global warming.”

“Action on climate and clean energy will not only motivate these key audiences to vote, it can help to generate excitement about Democratic candidates,” the memo concludes.

Inaction, on the other hand, runs the risk of depressing enthusiasm in the midterm election, a prospect that Democrats cannot afford if they hope to govern boldly for Joe Biden’s entire term. The results from past elections tell us that when Democrats fail to deliver on promises of progress, they suffer some of their most serious setbacks—as happened in 1994, during Bill Clinton’s first term, and in 2010, during Barack Obama’s first term.

The history doesn’t lie. Neither does the recent polling about what mobilizes young voters. The more Democrats bow to Joe Manchin’s demands, the more likely they are to lose the Congress in 2022, and the presidency in 2024.