I've read a lot of scenarios recently in which in which the Electoral College saves the day and prevents Trump from becoming President. The problem is that they neglect very serious collective action problems that are built into the structure of the Electoral College. I'm not saying you can't get around them, just that they pose genuine difficulties, and most people who write about the issue aren't paying enough attention to them.
Here's the basic idea: To deny Trump the presidency in the Electoral College, you need to create an unbreakable cartel of 37 Republican electors who were pledged to vote for Trump but who decide not to do so. (306-269=37). Democratic electors don't add anything to the cartel, because they don't reduce Trump's vote total.
The problem is that it's very hard to form such a cartel in the first place, and even if it does form it's pretty easy to cause people to defect from it.
For purposes of this blog post, let's put aside the very real concerns that the electors may be bound by state law, or that they will face legal sanctions if they don't vote for Trump, or that states will replace them as soon as they find out what they are up to. That's an interesting set of legal debates, but it's not central to my argument. Let's suppose that there are no such obstacles and that state law doesn't act as a disincentive to any elector. Let's assume that electors are perfectly free to vote for someone other than Trump if they think he would be a disaster.
Even so, you still have to form the cartel-- that is, an agreement among at least 37 Republican electors. It's hard to do this because the electors don't meet in a single location so they can't deliberate as a single body. This was a fateful decision by the Philadelphia Convention. They decided that it was too difficult to have the electors travel to the nation's capital to perform a single task (travel was very difficult and hazardous in those days); so instead they decided that each state's electors would meet separately in each state. This makes deliberation within state delegations easy, but deliberation across state delegations hard. (Compare Congress, which meets in one place, and in which such deliberations happen all the time.)
Fortunately, however, interstate travel is easy today, and we have telecommunications and the Internet. So deliberation across state lines is much, much easier than it was at the Founding. Even so, somebody has to arrange a meeting at which all or most of the relevant electors can deliberate and agree to form a cartel. And you need easily understood procedures and focal points to make it easy for electors to agree on a common course of action. (Thomas Schelling is smiling down from heaven at this point.) But in this case, there are no easily agreed-on procedures and focal points for collective action among the electors. (The lack of easily agreed-on focal points was one reason why it was so hard for Republicans to get rid of Trump during the primary season.)
Don't get me wrong: You could get around these organizational problems, but you'd have to start early enough. (Spoiler alert: nobody started early enough.).
In any case, suppose you surmount all of these obstacles. Suppose that 37 electors are able to form a cartel. They all agree to vote for a candidate other than Trump.
Then comes the next set of problems. Surely Trump is not oblivious to the fact that rogue electors are planning on forming a cartel to depose him. (It's in the papers every day!) Knowing this, it should be child's play for Trump or his people to pick off one or two members of the cartel with side deals. (For example, Trump could offer the elector something that would benefit the elector's home state, or he might promise to consider a certain policy, and so on.) Hasn't anybody read The Art of the Deal?
As soon as Trump makes a side deal with one of the 37, the cartel collapses, because Trump now has 270 electoral votes, and the other 36 get nothing. So everyone in the cartel has incentives to defect before the others do. That's yet another reason why these cartels are so hard to form in the first place. (And note as well that there is no sanction for defecting from the cartel--the rogue electors can't easily punish those who secretly promise to vote against Trump and then change their minds.)
The only way to keep Trump from peeling off one or two defectors is if the cartel is completely secret, so that Trump can't tell who is a rogue elector who will vote against him. That means he can't find out who to entice to defect. But if the cartel is secret, then it's even harder to organize the cartel in the first place.