In the year 2000, fresh out of college, I cast my second-ever presidential election vote for Ralph Nader. Later that night, I watched in horror as the contest between Al Gore and George W. Bush ended in an unprecedented electoral college toss-up, leading to a messy recount battle and the infamous Supreme Court decision Bush v. Gore. The chosen successor of a popular incumbent administration, Gore should have sailed to victory on the strength of the economy alone, yet he conceded the election to Bush, a candidate initially considered too unserious to be a true contender.

Gore lost Florida by 537 votes. Nader received almost 100,000 votes in Florida. And he actively campaigned in swing states, including Florida, in the lead-up to the election. If Nader had quit the race and thrown his support to the Democrats, we might be reminiscing about a Gore administration right now.

And I share the blame. Now, before you post mean things in the comments, let me clarify: I voted in New York state, which went blue in 2000, so my individual vote did not help swing the election. But I still feel complicit. I jumped on the Nader bandwagon and bought into a set of beliefs that seemed right to me at the time but were proven very wrong over the eight years that followed.

Chief among them, I thought that Gore and Bush were essentially indistinguishable. Carbon copies of each other. Both corporate insider candidates, beholden to big-money interests and out of touch with people struggling at the margins of the economy. I’m from the Rust Belt—I grew up near Cleveland—and I had seen factory closures turn a once-vibrant part of the country into a series of ghost towns. I blamed NAFTA and the Clinton administration’s failure to defend unions and stem the tide of outsourcing. In this and on other issues—welfare reform, prison sentencing—I thought the Clinton administration had bent so far backward to win over the right that it had lost its progressive conscience. The economy boomed during the Clinton years, but the gulf between the rich and poor, the haves and have-nots, only widened.

Nader voiced the discontent I was feeling. I was young and idealistic and wanted political revolution. It felt good to back a rabble-rouser, not the stiff, robotic Al Gore. I was annoyed with the Democrats for picking a predictable, incremental candidate who played not to the left, but to the mushy middle. I went to a Nader rally in NYC: Bill Murray, Michael Moore, and Susan Sarandon spoke. Eddie Vedder sang. I felt inspired, part of a movement to bring about real change, ready to cast my protest vote.

But here’s the thing: In the eight years that followed, I was reminded again and again that George Bush and Al Gore were not carbon copies of each other. Bush was a disastrous president. He got us into an expensive, unwinnable war that unleashed untold human misery both abroad and here at home. He cut taxes on the rich while failing to curtail spending, turning the $280 billion surplus he inherited from Clinton into a $6 trillion deficit. He relaxed gun control restrictions and refused to comply with international climate treaties. He passed No Child Left Behind, a law that turned schools into test-taking machines. He bungled the emergency response to Hurricane Katrina. His administration left the country mired in the biggest financial crisis since the Great Depression.

Gore might not have been a perfect president, but it’s likely he would have taken more reasonable action on the economy, climate change, and gun policy. It’s hard to say how he would have handled 9/11, but he might have been more cautious and more diplomatic in the Middle East than Bush was.

Now, 16 years later, I look back on my young, Nader-voting self and see plenty of parallels with the college students who are feeling the Bern. Hillary Clinton is a wonkish, often uninspiring candidate, just as Al Gore was. Like Gore, she promises to extend an incumbent’s centrist legacy rather than move the country further left. Her ties to the moneyed powers-that-be sometimes seem stronger than her connection to the other 99 percent. And Bernie, as Nader did, promises to dial back the influence of big-money corporate donors and bring about real change. He even has Bill Murray, Michael Moore, Susan Sarandon, and Eddie Vedder on his side.

But if Bernie splinters the left and erodes Clinton’s support among voters, the consequences for our country could be even more dire than another Bush administration. If the Bush administration was catastrophic, a Trump administration could be cataclysmic. He has no compunction about stirring up violent, hateful rhetoric among his supporters. He wants to deport millions of people and ban an entire religious group from entering the country. He threatens to shut down the press. If he gets elected, we’ll be counting down the days before he insults some world leader and starts World War III.

Alarmingly, some Sanders supporters seem to actually welcome the chaos of a Trump presidency: Susan Sarandon has said he can “bring the revolution,” an argument that only highlights her privileged position as a celebrity not at risk of getting deported, deployed, or discriminated against by a Trump administration. Jill Stein, running as the Green Party’s nominee, recently tweeted, “I will be horrified if Donald Trump is elected. I will also be horrified if Hillary Clinton is elected. Both are corporate politicians.” Change up the names, and she could be quoting her party mate Nader in 2000. Both Sarandon and Stein are ignoring real differences: Hillary Clinton may not be a revolutionary, but she’ll defend Roe v. Wade, preserve Obamacare, push for reasonable gun laws, protect LGBTQ rights, support parental leave, and heed climate science. Trump will do none of the above.

Like Gore, Hillary Clinton isn’t the left’s ideal candidate. But, barring a mathematical miracle, she’s our nominee. And, in what promises to be a tight general election, she’s going to need every vote she can get. Now that the Republican Party is consolidating around Trump, the Democrats’ failure to unify around its own presumptive nominee becomes all the more glaring. The longer Sanders stays in the race, the more Hillary’s negatives grow, and the more cash and attention she peels away from her general election efforts. A recent YouGov poll reports that 61 percent of Sanders supporters have an unfavorable opinion of Clinton, a number that has grown as the primaries continue to drag on. Moreover, Sanders’ critiques of Clinton have become more pointed and go beyond policy disputes; they also focus on process (allegations that the nomination process is rigged) and character (painting Clinton as corrupt and dishonest). Come November, it will be tough for the Democrats to energize voters who see their nominee as fundamentally untrustworthy and their party as unjust. Trump insulted practically every voting bloc in his party, and the GOP is still holding its nose to line up behind him. Yet the left threatens to fracture. How do we snatch defeat from the jaws of victory? Like this.

To the Bernie voters who are disgusted with the process and disillusioned with the Democratic nominee, I hear you. But if you plan to stay home, defect to a third party candidate, or vote Trump in November, think back to the fall of 2000. It only took 100,000 ideological purists in one state to give our country away to a know-nothing nightmare of a president.

Read more Slate coverage of the 2016 campaign.