At the start of the video, we're presented with two candidates, A and B, and shown the results of the election between them: seven for A, eight for B; a narrow win for B.
Then, the plot thickens, and a new candidate, C, who agrees on most issues with B, is introduced. Three of B's voters, and one of A's, decide they prefer C, and we are shown the TERRIBLE TRAGEDY of how C's presence caused A to win instead of B, a clear SUBVERSION OF THE DEMOCRATIC ORDER. And I agree; that's terrible. Adding a candidate who is not a winner themself should never change who the winner of the election is. Academically, this is called independence of irrelevant alternatives, or colloquially, the spoiler effect.
"Luckily" (according to the video), instant runoff voting saves the day, because it eliminates C, and redistributes their votes back to A and B, and the victory returns to it's proper place, with B.
But I have a question for FairVote.
What if C was just a bit more popular, and managed to convince just one more of B's supporter's to vote for them?
Now, B, having the fewest first-place votes, is the candidate who is eliminated. And, depending on B's voter's second-choices (which we don't ever see in video) either C or A may win. If two or more of the four prefer A over C, then A wins. Which is the same SUBVERSION OF THE DEMOCRATIC ORDER which instant runoff voting was supposed to guarantee never happened again; an "irrelevant alternative" changed the outcome of the election. That should never happen!
IRV's advocates are trying to popularize a false notion (or maybe they're just trying to deal with their cognitive dissonance) that there's some magic cutoff for "significance", beyond which a candidate doesn't count as a spoiler. But if it quacks like a duck, then it's a duck. I believe they may be confused because they (and all of us) are most familiar with plurality voting, and under plurality third parties virtually never get more than about 15% of the vote. There's a good reason for that value; it's that the difference between the Republican candidate and the Democratic candidate in any election is virtually never more than about 15% of the vote. Third parties tend to grow, until they get big enough that they spoil an election, and then they're destroyed in a terrible backlash (Nader has yet to recover from Gore's loss; come to think of it, neither has Ross Perot from Bush I's). The only thing IRV changes is what that cutoff-limit is; it goes from about 15% to closer to 30%. But don't let them trick you: it's still there, waiting for a fatted third-party to grow large enough to sacrifice itself upon its altar, and SUBVERT THE DEMOCRATIC ORDER by spoiling an election.
If you're an IRV advocate because you want to eliminate the spoiler effect, or because you want third-parties to have an actual chance of wining elections, then you should STOP being an IRV advocate. There are other voting methods that better achieve your ends. Score voting actually does completely eliminate the spoiler effect, which means third-parties have a real chance to win.