Voting is an exercise in compromise. Any winner has to get the most votes — i.e., the “first past the post” system. I may believe my old professor, my local police captain, my boss or my well-read uncle would make the best officeholder in any particular election. But writing them in would be useless, since no one gets into office on the strength of one vote.

First past the post means that in the majority of American elections, only two candidates stand a plausible chance of winning: the Democrat and the Republican.

Does this limit our options? Of course. But a better system doesn’t (yet) exist, which means that when you vote for a third party, you abdicate your right to affect the outcome.

Third parties will tell you that viability isn’t the point. Voting for them sends an unfiltered, uncompromised message that your views are not represented by Democrats or Republicans. Instinctively, that makes sense. Who’s to tell you to vote against your conscience? And if both candidates are equally objectionable, is there harm done if withholding your support from one helps elect the other?

One is always better than the other

The problem is, both candidates are rarely equally objectionable.

Sure, I’d find it difficult to choose in a race between Jihadi John and Kim Jong-un. But every election in the United States features viable candidates who possess differing (yet nonzero) levels of virtue and/or qualification.

And in every one of those contests, a well-read person will, despite all protestations to the contrary, have a preference — even if slim.

By voting third party, you are saying that you either a) are ignorant of differences between candidates or b) believe that letting the inferior candidate win is worth your political statement.

Spoiler effect

Third parties are a different story when the final outcome is a foregone conclusion. But in many elections, the “spoiler” effect isn’t theoretical. The presence of Ralph Nader and the Greens on the ballot in 2000 unquestionably handed the election to George W. Bush: According to the official results, Al Gore lost the state of Florida by 537 votes. Nader won 97,488 votes in total.

Since Nader voters would have gone for Gore in a two-person race (by roughly two-to-one), these ostensible liberals mathematically paved the way for a Republican presidency.

And say whatever else you like, but the country did not move further left in 2000 or 2004 due to the Nader voters — it moved to the right, with devastating effect.

Any similarly hoped-for message sent this year would be drowned out by a Trumpian cacophony of four to eight years.

Who really gains?

Yes, after time, George W. Bush was discredited and his party left the White House in shame. But it was Democrats, not Greens, who gained politically in the landslide victories of 2006 and 2008.

As a Democrat, I recall those victories fondly. Yet somehow I think I’d have recalled the Al Gore presidency with even more fondness. Because on the way to 2006 and 2008, we experienced in the Bush Administration a case study in squandering prosperity, human life and international goodwill — i.e., events not worth voting Nader to “make a statement.”

Democrats would gain too from the inevitable disaster of a Donald Trump administration. The reality is that the Libertarians and Greens are not well-organized enough to capitalize on the assumed unpopularity which Trump would generate. Gary Johnson and Jill Stein know this, yet continue to run vanity personal candidacies, expending resources on what could otherwise be a grassroots movement focusing on winnable local elections.

Some more radical third-party acolytes may actually be hoping that a Trump presidency will discredit all of our national political institutions to such an extent that it will open up space for their niche movements. But the road there (by explicit design!) requires more suffering, injustice, instability, reputational damage and general decline than ever seen before in American history. Do you really think that’s worth it?

History has shown the resilience of the two-party system, despite enormous political tribulations since 1860. Every third-party “moment” since then has proven to be merely that — see the fates of the Reform Party, American Independents, Dixiecrats and Progressives.

To stop Trump, vote Clinton

So what to do in this election if you’re struggling with the choice? The obvious decision, given the Republican candidate, is to vote for Hillary Clinton, however begrudgingly.

Are you a Bernie Sanders supporter? If you truly care, as I do, about the issues he championed, you cannot equate someone who is (at worst) pandering to progressives with a proud reactionary. Nor can you claim to have trusted the judgment of Bernie Sanders and ignore his unequivocal endorsement of Secretary Clinton.

Then there are the “Never Trump” Republicans who claim to be unwilling to hand the keys over to their nominee — but won’t vote for Clinton. These people may be honest in their disdain for Trump, but simply do not care enough to stop him.

Consider the damage he would do to American credibility, the power he would wield in America’s nuclear arsenal, the risk of global trade wars, his affinity for Vladimir Putin or his plan (still on his website) to ban all Muslims from entering the United States. Is someone who is just kind of liberal the equivalent of all that (and more)?

If you can’t acknowledge there is a difference, you’ve been tacitly okay with Trump the whole time.

If you’re a disgruntled Republican considering voting for Gary Johnson, remember: A high Johnson turnout will actually preclude the partywide soul-searching you’re looking for. The defectors, rather than the man at the top of the ticket, will be blamed for the defeat.

And for the true libertarians: I know you think Democrats are all about big government. But in order to equate Hillary Clinton and Donald Trump, you have to believe that a bloated public sector is as dangerous as a white nationalist holding the nuclear codes. Forget his theoretical positions on criminal justice, policing, torture and surveillance — think about the issues of personal freedom you hold dear and imagine how Trump’s reaction to a latter-day 9/11 would materially imperil that liberty. Having made a statement about small government in the voting booth won’t feel so good then.

Defeating Trump is an all-hands-on-deck moment for American democracy. Trump fans will no doubt disagree. But for those with serious doubts as to the fitness of this man to the highest office in the world, the required countermove is voting for Hillary Clinton. It doesn’t mean you must be a Democrat. It doesn’t mean you have to support her policies or support her personal life. It doesn’t mean you have to vote for her in 2020. But it does mean you are not willing to countenance an American Mussolini running the show — no matter what.