A village on the island of Java, in Indonesia, experiences flooding linked to rises in sea levels. Photograph by Pradita Utana / NurPhoto / Getty

In August, 2015, when President Obama announced the final version of the Clean Power Plan—the centerpiece of his effort to combat climate change—he quoted a speech that Martin Luther King, Jr., gave at Riverside Church, in April, 1967, opposing the Vietnam War. “I believe ‘there is such a thing as being too late,’ ” the President said, in a ceremony in the East Room. He liked the line so much that he repeated it, a few months later, at the opening of the international climate negotiations, in Paris: “For I believe, in the words of Dr. Martin Luther King, Jr., that there is such a thing as being too late. And when it comes to climate change, that hour is almost upon us.” Speaking about climate change this past summer, in Yosemite National Park, he invoked it a third time.

The line came to mind yet again this week, when oral arguments against the Clean Power Plan were heard in the Court of Appeals for the District of Columbia Circuit. Twenty-seven states, led by West Virginia, together with a passel of oil and coal companies, have sued the Environmental Protection Agency to prevent the plan from going into effect. There is, indeed, such a thing as being too late, and the plan’s opponents—who were the very folks who made the plan necessary—seem determined to delay until that point, and perhaps beyond it. As Dr. King observed, in a context that was at once very different and not so different, procrastination is “the thief of time.”

Depending on how you look at things, the Clean Power Plan is either extraordinarily complex—the final rules take up more than fifteen hundred pages—or pretty straightforward. Basically, the plan requires each state to figure out a way to reduce the carbon-dioxide emissions from its power plants. Because each state is starting out with a different energy mix, each one has been given a different goal; those that now rely heavily on carbon-intensive coal are subject to less stringent restrictions than those that are starting out with more natural-gas plants or wind turbines. It could be contended that this approach penalizes precisely those states that have done the most to reduce their emissions, but, for the most part, it’s the states that have made the least effort that are now suing.

All in all, the plan is supposed to reduce emissions from the nation’s power sector by about thirty per cent by 2030. (This is using a baseline of 2005 emissions.) The plan is central to the commitments made by the United States at last year’s climate conference in Paris. Without the power-sector reductions, it will be pretty much impossible for the country to live up to its pledges, and if the U.S. doesn’t live up to its pledges then it’s unlikely other countries will, either, and—well, you get the picture. As William Ruckelshaus and William K. Reilly, both Republicans and both former E.P.A. heads, noted in an Op-Ed in support of the plan that ran in the Times on Monday, “the consequences will be drastic if the United States and other countries do nothing.”

The plan’s history already reads like a legal thriller. In February, the Supreme Court blocked the implementation of the regulations, pending the resolution of the litigation. The ruling was extremely unusual, especially as the Circuit Court had unanimously declined to issue a stay; as Richard Revesz, a professor at the New York University School of Law, recently told my colleague Jeffrey Toobin, “It was totally unprecedented for the Supreme Court to step in.” The 5–4 vote on the stay seemed, to put it mildly, to bode ill for the plan. Then, a week after the ruling, Justice Antonin Scalia was found dead in his room at a Texas ranch. Suddenly, the plan’s prospects improved.

A three-judge panel of the Circuit Court was supposed to hear oral arguments in West Virginia v. Environmental Protection Agency in June. But the arguments were postponed until September so that all eleven judges could consider the case. (The court’s chief judge, Merrick Garland, Obama’s appointee to fill Scalia’s seat, who remains in confirmation limbo, recused himself, so only ten judges were present for the arguments on Tuesday.) Even opponents of the plan seem to expect that the Circuit Court will rule in the E.P.A.’s favor, although no one really knows what the decision will be, or when it will be handed down. And whatever the outcome at the Circuit Court level, the case seems destined to be appealed to the Supreme Court, which, it’s assumed, in its current configuration would split 4–4 on the issue. Such a split would leave the lower court’s decision in place.

Which brings us, as so many things do these days, to the Presidential election. Donald Trump, who has very publicly called climate change a “hoax” (despite very publicly denying having done so, in Monday’s debate), has said that he will “rescind” the Clean Power Plan. Hillary Clinton, in contrast, has said that she will carry it out. Whoever is elected will, it seems, have the chance to nominate the deciding Justice to the Supreme Court. This could be seen as yet another reason to be terrified of a Trump victory. Or it could be seen as the reason to be terrified of a Trump victory. If the next four years are spent rolling back whatever progress has been made on emissions, then almost certainly the temperature targets that world leaders set last year in Paris will be breached. In fact, even if the next four years are spent making more progress, it’s likely that the targets will be breached. In the case of climate change, to borrow from Dr. King once again, tomorrow really is today.