What About Write-Ins?
Between the Bernie Bros. and the NeverTrump folks, there's a lot of talk about write-in votes this year. Based on past experience, it is likely that most of the people threatening this course of action won't actually do it, and will either line up behind the major party candidate they find less odious, or will choose a third party to vote for (Libertarian Gary Johnson for most right-leaning types, Green Jill Stein for left-leaners). For those who really do attempt a write-in, though, what will happen?
The answer to that varies by the state in which the voter resides. Seven states—Arkansas, Hawaii, Louisiana, Mississippi, Nevada, Oklahoma, South Dakota—do not allow write-ins at all. So would-be writers in who live in those places are out of luck. On the other side of the spectrum are eight states—Alabama, Delaware, Iowa, New Hampshire, New Jersey, Oregon, Vermont, and Wyoming—that will allow voters to write-in any name their heart desires. In those locales, Mickey Mouse, Ringo Starr, Darth Vader, Pat Paulsen, and Vermin Supreme (with his platform of zombie apocalypse awareness, time travel research, and a free pony for every American) are all fair game. In the remaining 35 states, the only acceptable write-in candidates are those who have officially registered with the state by some stated cutoff date, either by filing paperwork, paying a fee, collecting signatures, or some combination of the above.
Assuming that a voter casts a legal write-in vote (which, again, can be done in only 43 states), what are the implications? As a practical matter, there are three. The first is that the voters deprive the legitimate candidate they were most likely to support of a vote, thus helping their opponent. So, a write-in for Sen. Bernie Sanders (I-VT) de facto helps Donald Trump by depriving Hillary Clinton of a vote that she otherwise would likely have claimed. A write-in for Mitt Romney does the same, helping Clinton at Trump's expense.
The second implication of a write-in is that the voter makes a protest statement. If many other people do the same, it might make a very, very small impression. For example, if thousands of people write in Mitt Romney's name, that might send a message to the GOP establishment (albeit a message they pretty much already agree with). However, keeping in mind that Romney will not be an "official" write-in candidate, it means that there are only eight states in which this possibility exists. The same, of course, applies to Sanders' write-in votes; in both cases such votes would be automatically discarded in nearly all states. If thousands of Utahns expect to see headlines about how many votes Romney got, or thousands of Floridians expect to see the same for Sanders, they are going to be sorely disappointed. In most states, the legal write-in votes will be matched by only a handful of other voters. And 1,000 people voting for a minor or unknown candidate is not a "statement," it's a lunatic fringe.
The third and final implication of write-in votes, one that voters do not care about but poll workers do, is that they create a lot of extra work for the ballot-counters. A write-in ballot has to be separated out, hand-tallied, and usually has to have some sort of special form completed. So, a voter who is on the fence about this kind of protest might want to think about sparing these civic-minded volunteers another headache on a day that will be full of them. It will also slow down the count and reporting, annoying millions of people waiting for the results.
Now, what about the incredibly remote possibility that a write-in candidate actually wins a state (or, in the case of Nebraska or Maine, a congressional district) and is entitled to presidential electors? Well, given the low likelihood of this possibility, it was never contemplated by the Founding Fathers, and it's never actually happened. Consequently, the Constitution is largely silent on the matter, as is existing case law. Many of the states that require write-in candidates to declare themselves (like, say, Texas) also require them to submit lists of electors. So, there would be no problem in those places, nor in the seven states where write-ins aren't allowed. But there are a couple of dozen states where, for one reason or a another, a write-in candidate is unattached to a slate of electors. It is in those states that we'd be left in a legal gray area if a write-in were to win.
Let's use a Sanders write-in win in New Hampshire as a hypothetical example. In this eventuality, he would be entitled to four electoral votes. Among the handful of scholars who have pondered this question, a few have suggested that the victorious candidate could serve as their own elector or electors. According to this theory, a write-in candidate who won New Hampshire could cast 4 electoral votes for themselves, by themselves. This way of thinking does not seem to square with the wording of the Constitution, however, which clearly envisions separate individuals being chosen to represent each electoral vote. Further, as an officeholder at the federal level, Sanders is forbidden from serving as an elector, whether on his own behalf or someone else's. So that is off the table for him, and probably for any other candidate, as well.
This being the case, who would choose electors on a successful write-in candidate's behalf? The Constitution places that decision in the hands of the state legislatures, which in turn have handed the privilege over to the state parties and their conventions or central committees. If Bernie Sanders had even the remotest chance of winning New Hampshire, the smart decision would be to quickly call a "convention" of his supporters and to choose electors before Election Day. This would be virtually unimpeachable, from a legal standpoint.
If this did not happen, however—say, in the case of a complete surprise victory—then it could get dicey, depending on the circumstances. In most scenarios, those four votes would not matter, and the New Hampshire legislature would likely let Sanders choose his electors post hoc, or else would appoint loyal electors on his behalf. But if those four votes were somehow enough to swing the election, the New Hampshire legislature might try to assert itself with the idea of appointing "faithless" Sanders electors who would actually vote for Hillary Clinton. Of course, Sanders would fight back, taking the matter all the way to the Supreme Court, if need be. Where, at the moment, there's every chance of a 4-4 deadlock. At that point, it would likely turn into a game of political horse trading, as it did in 1876, when—in an election decided by a small number of disputed electoral votes—Democrats traded the presidency for an agreement to end Reconstruction. This would make for fine political theater, but would be very bad for the democracy, so it's probably for the best that this is extremely unlikely to happen.