“We won’t see a presidential candidate like Bernie again in our lifetimes.” As I heard these words, spoken by a woman at a Sanders campaign event recently, I felt a chill go through me. Because I knew she was right. We won’t.

We won’t see another presidential candidate who refuses to take campaign donations from the wealthy and the corporate elite. We won’t see another candidate with the courage to take on Wall Street. We won’t see a candidate with the guts to tell the American people that they have lost their democracy. We won’t see another candidate who mentions the working class and the poor in his speeches. We won’t see another candidate sounding the alarm bells over global warming.

It is no wonder that the wealthy owners of the New York Times and Washington Post and other media organs have reacted to Sanders’ insurgency with such fury, emptying their stables of talent each day in an effort to run him down and exterminate him politically. It’s like watching the Wicked Witch in The Wizard of Oz, standing in the window of her castle, arms outstretched, sending her flying monkeys hurtling through the sky on a mission to destroy her would-be destroyers.

Just this morning, the day after Sanders crushed Clinton in the Wisconsin primary by 13 percentage points—his seventh win out of the last eight caucuses and primaries—the New York Times published a front page article on the results that included only a single, one-sentence reference to Sanders (falsely claiming that the race in Wisconsin had been “close”). That was all. Every other word in the 1500-word news story was about Ted Cruz’s victory over Trump in the state.

In a normal election year, the fact that an avowed “democratic socialist” was routinely winning Democratic contests in states like Washington, Minnesota, Hawaii, and Wisconsin, or that he was raising far more money, from small individual donations, than an establishment candidate drawing on the vast resources and connections of her national party, would have been huge front page news.

But this is not a normal election year. It’s the end game. It is a crisis, in the original sense of the ancient Greek word, krisis—the turning point in an illness when a patient either dies, or recovers. Except that the patient, in this case, is both the American body politic and the living earth itself.

Global temperatures in February smashed all previous records, putting 2016 on track to be even hotter than 2015—previously the hottest year on record. Not only didn’t we humans reduce our carbon emissions last year, we increased them--and at a greater rate than ever recorded. As Piers Tan, a leading climate scientist at the National Oceanic and Atmospheric Administration observed, “Carbon dioxide levels are increasing faster than they have in hundreds of thousands of years.”

Just four months after the supposedly historic climate talks in Paris, then, the world is plunging headlong toward a full-scale ecological meltdown. Drought, flood, fire, monster storms, acidification of the oceans, disappearing fresh water, the migration of tropical diseases into the northern hemisphere, pandemics, accelerating species loss—we’re just at the beginning of things. Crops and agriculture will fail. Billions of people will lose their homes and even nations. Whole regions of the earth may become uninhabitable.

Last week, scientists at NASA issued a stunning new estimate about the West Antarctic ice sheet: it’s melting at a far greater pace than earlier studies suggested. Just a few years ago, climate experts at the United Nations warned that the oceans could rise as much as two to three feet by the end of the century. Such a rise was then considered the worst case scenario—a true calamity to be avoided. The new study suggests that sea levels could instead rise as much as five or six feet. That means that dozens of world cities—New York, Philadelphia, Tokyo, Hong Kong, Dhaka, Cape Town, Bangkok, Alexandria, among numerous others—will be swallowed by the sea in our children’s lifetimes.

But the problem isn’t just global warming. The entire biosphere of the earth is coming violently apart. Thousands of species across the phylogenetic spectrum are disappearing. The oceans are becoming acidic. Billions of sea animals are being “mined” from the sea, tearing the oceanic food web to shreds. The very fabric of life on earth is being destroyed.

Does this sound bad? It is beyond bad. If it is not literally the end of the world, it is certainly the beginning of the end of a livable world. For two million years, the earth has been an amazing, beautiful, bountiful place for our species. It is the only home we will ever know or ever have. Now, the writing of impending calamity is on the wall—it’s just in letters so big that most people can't see them.

Liberals planning to vote for Hillary don’t seem to grasp what is really at stake in this election. They imagine that the worst thing in the world would be to have Donald Trump in the White House. But they’re not exercising their imaginations enough. This election is about far, far more than stopping the Republicans, as important as that is. It’s about interrupting the system of global wealth accumulation before it destroys all life on earth.

There are many reasons to find Hillary Clinton repugnant as a politician: her support for the Iraq War in 2003 and for the Honduran military coup in 2009, her ties to Goldman Sachs and Big Pharma, her support for neoliberal trade and economic policies that hurt working people, children, and the poor, her depiction of Edward Snowden as a “traitor,” her support for fracking, her past mockery of the women who accused her husband of sexual assault, and so on. But the worst thing about Hillary is simply that she represents the status quo.

Perhaps, twenty or thirty years ago, it was still plausible to argue that voting for “the lesser evil” might usher in the kind of changes that our society desperately needs. But not today. Not with fascism rising again in Europe, and perhaps now even here in the United States. Not with the hollowing out of our democracy by corporate money. Not in the face of an unprecedented ecological emergency. If a Trump presidency is unthinkable, a Clinton presidency is unacceptable.

Critics of Sanders dismiss his policy proposals, like a single-payer health care system or free higher education (rights long ago established in Europe) as “pie in the sky.” But in reality, it is Clinton’s supporters who are engaging in wishful thinking. Last month, Oxfam reported that the richest 62 individuals now own as much wealth as the poorest 3,500,000,000 human beings, half of the whole species. To believe that such a system can be “reformed,” or that Hillary will give us the “incremental change” we need to disrupt this monumental theft of the world’s resources, is dangerous self-delusion.

Yes, the 2016 presidential race is still about Democrats and Republicans. But it has also become a national referendum on capitalism. For the first time in modern memory, Americans are being given the rare opportunity to affirm, or to reject, the trajectory of their economic and political system.

It would be hard to exaggerate how much is at stake in the coming weeks. Think of the world system as an ocean liner, steaming toward a field of icebergs. Liberals in the key primary states of New York, Pennsylvania, and California will soon be given a historic choice: either to keep the ship on its present heading, toward the icefield, or to set the ship on a new course.

The latter course represents Bernie Sanders. It poses its own risks and uncertainties. Sanders may not be able to pass the initiatives he now wants to. Powerful forces in our society will set about to undermine his presidency. Sanders himself is imperfect, and he will make mistakes all his own. But it is far better to embrace an uncertain future than a doomed one.