Judging from my Facebook page, the internet is blowing up with arguments that, in November's election, voters must cast their ballots for a major-party candidate even if they dislike that candidate, and they must not vote for a third-party candidate.
These arguments go like this:
Third-party voters say neither major-party presidential candidate is worthy of their vote. But in fact, [major-party candidate the writer supports] is not nearly as objectionable as [other major-party candidate]. If [other major-party candidate] wins, terrible things will happen, but if [major-party candidate the writer supports] wins, terrible things won't happen. So stop selfishly thinking about a third-party candidate, and cast your ballot for [major-party candidate the writer supports]!
No doubt this argument is appealing to the writer and other major-party backers. But even if we grant the writers' assertion about the virtues of their preferred candidate AND their belief that a third-party candidate can't win the presidency, this argument literally is irrational and--worse--it deprives voting of perhaps its greatest virtue.
The Real Clear Politics "Battle for White House" electoral map currently shows only 13 states, plus one Maine congressional district, to be toss-ups in the presidential race. Six more are rated as "leaning" toward Democrat Hillary Clinton and six (plus a Nebraska congressional district) are leaning toward Republican Donald Trump. RCP categorizes the other 25 states and the District of Columbia as being "solidly" (or stronger) in either the Clinton or Trump columns.
For those latter 25 states plus D.C., a would-be third-party voter's grudging ballot for a major-party candidate is literally meaningless in deciding the presidency. The state's Electoral College electors will go to Clinton or Trump regardless of how that voter casts his or her ballot--and the voter certainly must know that. So if that person chose to forgo voting for a third-party candidate and instead voted for a major-party candidate anyway, that voter made an irrational decision.
What about the other 25 states? Yes, there is a possibility that a voter's ballot could matter—but only if that voter's state (or congressional district, in the states where electors are awarded by distict) popular vote is perfectly evenly divided +/– one vote , and the national electoral college is decided by that state's (or district's) Electoral College electors. (Notice the qualifier "only if," which means there are still more conditions that need to be met in order for the one ballot to prove pivotal.) In this case, the probability that the voter's ballot would be meaningful isn't zero, but it practically is. So, if a person in these states chose to forgo voting for a third-party candidate and instead voted for a major-party candidate anyway, that voter made an irrational decision.
Does this mean that people shouldn't vote for president? It does if their sole motivation is to cast the deciding ballot. Voting has costs in time and money (e.g., gas money, bus fare), and it is pointless to absorb those costs for no benefit.
But there is a sound reason to vote (for some people, at least): for the pleasure of expressing one's political preference. If voting for one of the major-party candidates provides that pleasure, then the voter should do it. For some voters, third-party candidates provide that pleasure because third parties are strongly associated with specific political causes (e.g., liberty, the environment, federalism) that many people care about deeply. Expending time and money to enjoy that pleasure is as sensible as spending time and money for the pleasure of reading a good book, or watching a baseball game, or eating chocolate.
So if a person wants to vote for Jill Stein in order to signal concern for the environment and disgust with the major party candidates, it's perfectly sensible to do so. The same is true for the person who wants to vote for Gary Johnson to show support for individual liberty and free markets. It's even sensible to vote for the perennial write-in favorite Mickey Mouse, to indicate dissatisfaction with American politics. And, of course, one can always follow H.L. Mencken's advice and not vote at all.