Page "Spoiler effect" Paragraph 5

Arrow's impossibility theorem states that rank-voting systems are unable to satisfy the independence of irrelevant alternatives criterion without exhibiting other undesirable properties as a consequence.

However, different voting systems are affected to a greater or lesser extent by IIA failure.

For example, instant runoff voting is considered to have less frequent IIA failure than First Past the Post ( also known as Plurality Rule ).

The independence of Smith-dominated alternatives ( ISDA ) criterion is much weaker than IIA ; unlike IIA, some ranked-ballot voting methods can pass ISDA.