Lesser of Two Evils?

Scales of Justice
On both sides of this election, I have heard the same thing: “I don’t like ________, but I just can’t bring myself to vote for the other candidate.”

On the Right, are people who think Trump is a terrible candidate and really unworthy of the White House, except we can’t let Hillary Clinton win. On the Left, same thing in reverse – Hillary isn’t a great candidate, but Trump is so much worse.

What about this argument …

Which candidate is the lesser evil?

Are we expected to vote for the lesser of two evils?