I sat and did a spreadsheet over a three-way race (Trump, Bloomberg, and Hillary).....if this were to happen (I think it's less than a 20-percent now, and more likely Mr Big-Gulp himself would enter at the last minute at the Democratic Convention to replace Hillary).
In a three-way deal....I don't think any of the three would be able to take the 270 Electoral College votes necessary to win. I think Bloomberg would win three to five states, and thus create the 270-problem.
So as a reminder....if you fail to reach 270 Electoral Votes....then it's dismissed and they meet a week later in DC, for the House to elect.....state by state.....with one vote each.....the next President (they would have all three to vote upon). The Senate would meet and then vote from the top two VP candidates for VP (creating a possible situation where a Democrat VP is working for a Republican President).
Three state delegations are split in number (equal Republicans and Democrats), and it's doubtful that they would be able to reach some conclusion.....so they don't count (Maine, NJ, and Minn).
Republican-led states lead with 33 states....more than enough if the Republicans stood by Trump. I doubt that the Party apparatus would do that.....so you can figure some issues here.
Trump is smart enough to convey his direction ahead and where you have a small state.....say less than four members in the Republican group of 33.....Trump might be able to promise enough.....to get their votes. So, I'm giving Trump roughly sixteen to eighteen states. Hillary would be able to carve out fourteen states, unless the Democratic Party abandons her. So Mr Big-Gulp would be there with seventeen states.
None of this equals 26 votes.....as required to get over the hump.
One could sense.....if we into this big of a mess and after one day of talking, and one real vote by the end of day one.....that this might take a week.....maybe two weeks, with people demanding all kinds of promises from their party, or for their state. You might suddenly find that Trump's talents of promising thing and delivering.....has some benefit. Maybe you could convince six Democrats from Florida to flip their votes among the state members over to Trump, or talk 15 House members from Texas to flip over.
Would this trigger people to go anti-Electoral College and demand a Constitutional change? Maybe. But you'd have to ask......who got the idea to fake out people from both the Republican and Democratic parties? Who really would want Mr Big-Gulp as president?