Disaffected Republicans, Democrats and independents have taken to write-in voting in an expression of their frustration. From Ballot Access News:

The Washington Post has this article about write-ins in presidential elections, with an emphasis on how popular it seems to be this year. If Gary Johnson or Jill Stein poll approximately 5% of the national vote, the precise national percentage may need to be determined. The question of whether write-in votes cast for presidential candidates who have no slates of presidential elector candidates standing behind them may need to be adjudicated. The denominator (the number of valid votes cast for president in the entire U.S.) might vary according to how that question is answered. Another question might be whether votes cast for “None of these candidates” in Nevada are valid votes. A good case can be made that they are not valid votes, because there are no presidential elector candidates represented by such a vote.

According to the Washington Post:

“It’s literally impossible to win a presidential election through a write-in vote,” said Jan Baran, an elections lawyer with the Washington firm of Wiley Rein. That’s because of the patchwork of rules governing how write-in votes are counted or whether they are even allowed at all. Nine states don’t permit write-in voting for the presidential race.