> Reforms like instant runoff voting make third parties more viable by eliminating spoiler effects.

IRV doesn't eliminate spoiler effects, it just makes them more complex by creating more points where they apply.

It also isn't at all good among single-winner ranked-ballots methods for making more parties viable, and in any case, the by-far best way to make more parties viable is to have legislative elections not run in winner-take-all races, but in multiseat races with an election method that has proportional results (STV in small multimember districts is the easiest candidate focussed system. Party List PR at the whole-legislature level is what most peoole think of when you hear “proportional” systems, and there are a large number of alternatives that are largely in-between those poles in some sense.)