With his decisive victory in the Nevada caucuses on Saturday, Vermont Sen. Bernie Sanders became the clear frontrunner for the Democratic nomination. And the panic commenced almost immediately.

Among center-left Democrats, the fear is that a self-proclaimed democratic socialist can't possibly win a general election contest against President Trump. Never Trump conservatives say they agree, but the intensity of their agonizing belies their focus on the horserace. For these erstwhile Republicans, the greater fear is that Sanders might actually win.

That's why we've already begun to hear a lament that's bound to be repeated as long as Sanders looks on track to secure the nomination — and if he becomes the nominee, all the way down to Election Day. The lament goes like this: "I loathe Trump, think he's terrible for the country, and planned on trying to defeat him in 2020 by voting for the Democratic nominee. But Sanders is a bridge too far. I can't possibly cast a ballot for him. Which means I may well need to hold my nose and vote for Trump after all."

To which the proper response is: Don't be ridiculous.

There is no legal or moral imperative to vote. If you think Trump is an atrocious president — so bad, in fact, that you've ditched your own party and publicly vowed to work for the victory of the opposition — why on Earth would you reverse yourself just because you can't in good conscience support the man running against him? In a situation like that, the best path forward is obvious: Just say no to both.

Too often those of us who think and write about politics for a living treat voting as some kind of necessity of civic life — a privilege so precious that it must be exercised regardless of the circumstances. To refrain from voting is a serious failing, a shirking of political responsibility so grave that it justly earns the shirker a penalty of shame and opprobrium.

But that isn't true. All things being equal, voting is a good thing. But all things aren't always equal. Sometimes the choice before us is so unsavory that not voting is preferable to pulling the lever. To hold otherwise is to imagine something absurd and obscene: a proverbial gun put to our heads requiring us to choose between the options before us, no matter how bad we consider them to be, demanding we cast a ballot for one or the other, with no third option available.

But of course there is always a third way, even if there's no third party or candidate. (I'll return below to the question of what to do when there is a third party or candidate to choose from.) The third way is simple: Refuse to vote for either candidate. Don't vote for the corrupt, incompetent demagogue and aspiring authoritarian — or for the socialist ranter and raver with a soft spot for communist dictatorships. Go ahead, keep your hands clean. Express your preference by refusing to endorse either of the two bad options. When you choose not to choose, you still have made a choice.

Now, I want to be clear: I will never vote for Trump, but I haven't made up my mind about Sanders (assuming that he really ends up as the nominee). This isn't a column about me. It's about people who have expressed a strong and well-founded antipathy toward Trump acting as if their possibly equal or greater antipathy for Sanders necessitates that they announce an intention to reverse themselves on the president.

There is no such necessity.

But what if there's a third party candidate available — say, Michael Bloomberg or some other centrist option who runs as an independent in the general election? For voters strongly opposed to both Trump and Sanders, this would seem to be an ideal solution. Now their supposed civic duty to vote can be fulfilled without requiring a compromise of conscience.

Except for one problem: America's electoral system nearly always turns third-party candidates into spoilers. They almost always lose — and in so doing they weaken the candidate closer to them on the ideological spectrum. At least that's the way it works when the third-party candidate is more ideologically extreme than the major-party options. So, for example, Ralph Nader's left-wing Green Party presidential campaign in 2000 drew votes from center-left Democrat Al Gore, helping to ensure the victory of center-right Republican George W. Bush. That makes voting for a third-party candidate extremely dicey.

But what about the possibility of a centrist challenge in 2020? There the electoral logic is murkier. Bloomberg or another centrist would presumably oppose both major-party candidates and stand between them ideologically. Would he draw more votes away from Sanders or Trump? That's an exceedingly complex question that would be quite difficult to game out before votes were cast.

Then there's the possibility of this third-party candidate not merely tipping states unpredictably one way or the other between the major-party options but actually carrying states. If that happened, it could easily produce a situation in which none of the three candidates reached the 270 electoral votes required to prevail. And that could produce a level of chaos — with the election ultimately decided by a partisan vote in the House of Representatives — that would be exceedingly bad for the country.

All of which means that the best choice when faced with two bad options in an election may well be to sit out the contest altogether.

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