This example shows what happened when voters naively supported their favorite in an IRV election. This is a simplification of an actual 2009 mayoral election in Burlington, Vermont, USA. The actual first-round totals were as follows. You can find a more complete analysis with all the data here.
In this election, Wright was the IRV spoiler. In this election, IRV eliminated Montroll who had the least first-choice votes. This elimination sent Kiss and Wright to the final round where Kiss won with more first-choice votes. Wright can’t win against Montroll or Kiss in a one-on-one election. Wright’s sole role is as a spoiler, changing the election outcome. Interestingly, Montroll is able to beat both Kiss and Wright one-on-one (a Condorcet winner). But IRV did not pick Montroll.
The row highlighted in green represents the voters who could have gotten a better result by insincerely top-ranking their second choice, Montroll, as first.
(Montroll=Democrat, Kiss=Progressive, Wright=Republican).
# of voters Their ranking
This election was a bit interesting in that a Republican, a major party in the US, played the role of spoiler. It just happens that Burlington is a very liberal town where the Progressive Party is more popular than the Republican Party. For a growing traditional third party, Burlington’s IRV lesson plays out in exactly the same way.