If Trump doesn't win the Republican nomination, does he run a write-in campaign?

[Orser67]

Obviously it's a question inviting speculation, but at this point I think that there is a)a serious chance that Trump doesn't win the nomination and b)a serious chance that a Trump write-in campaign has an effect on the 2016 election. According to this article, 43 states allow for write-in candidates, and according to this Daily Kos Elections blog, the seven states that don't are Hawaii, Nevada, South Dakota, Oklahoma, Arkansas, Louisiana, and Mississippi.

Here's a map that shows the states he could target. States that don't allow write-in campaigns are in grey (except Hawaii), while states that gave over 55% of their vote to Obama are in red. Utah is in blue because Trump seems to have a unique lack of appeal in that state.

[Orser67]

No, because he can still run as an independent in a majority of states. Most states final deadlines for ballot access are after the convention. If it becomes clear he won't be the nominee earlier, he could get on the ballot in even more places. If it looks like the RNC might deny him the nomination, he will probably start filling in the early states as a threat to the delegates. Ballotpedia has a list of deadlines, btw.

His optimal course of action is to run as an independent in some states and as a write-in candidate in some others, depending on the logistics.
For example, it's almost impossible to run as an independent in Texas but it's actually pretty easy to run as write-in. In some other state the opposite might be true.

The Texas sore loser law bars write-in campaigns too. Trump absolutely cannot run in Texas.

He could mount a legal campaign to try to overturn the sore loser law. According to "minor political party activist" Richard Winger: sore loser laws can’t apply to the presidential race because people who cast ballots in the general election aren't voting for a candidate, they're choosing electors — members of the Electoral College — who have pledged to support that same candidate.

I'm imagining Trump's legal challenge going all the way to the Supreme Court, which in turn deadlocks 4-4.

[Orser67]

Personally, I think if Trump lost the nomination, he would run an unofficial write-in campaign designed to sabotage the Republican Party. He wouldn't have any chance of winning, but he would be able to semi-campaign for the remainder of the general election and he would have the chance to stick it to the Republican Party.

However, I find it highly unlikely that the Supreme Court would have any interest in taking up that particular claim as it's really just a state law issue of statutory interpretation.

Now I personally think there are First and Fourteenth Amendment grounds for challenging the constitutionality of sore loser laws, but the 1974 Supreme Court case Storer v. Brown seems to say I'm wrong.   

Perhaps, but Williams v. Rhodes did set the precedent of the court stepping into protect independent ballot access on the grounds of the Equal Protection Clause. I also wonder if an an analogy could be drawn to U.S. Term Limits, Inc. v. Thornton, when the court struck down an Arkansas law preventing ballot access for Congressional candidates who had served three terms in Congress. I'm not saying that the court will overrule Storer, but if they did take up the case, I don't think it would be totally unjustified in precedent.