Consider a simplified approximate version of the 2000 US Presidential election. Here's approximately how (poll studies showed) the voters felt.
| #voters | true favorite |
|---|---|
| Bush(Rep) | 43% |
| Gore(Dem) | 30% |
| Nader | 27% |
But the Nader-favorite voters, if forced to choose between Gore and Bush, favored Gore by about an 80:20 ratio. It was strategically stupid of them to vote honestly for their true favorite Nader. If they did so, as we can see, their most-hated candidate (Bush) would win easily. If every Nader voter instead refused to vote for Nader, then approximately this would have happened:
| #voters | their vote |
|---|---|
| Bush(Rep) | 49% |
| Gore(Dem) | 51% |
And Gore wins, which – in the view of about 80% of the Nader voters – was a better outcome. Our plurality voting system incentivizes voters to lie. And not only that, but to lie in such a way that "third parties" systematically are weakened and die.
So sure enough (studies showed) about 90% of the Nader-favorite voters did vote for somebody else! (How would you feel about that if you were Nader?) Here's how it went down (official election totals)
| #voters | true favorite |
|---|---|
| Bush(Rep) | 47.9% |
| Gore(Dem) | 48.4% |
| Nader | 2.7% |
| Others (combined) | 1.0% |
and Bush won. (Yes, Bush won with slightly fewer votes than Gore, thanks to his extremely close victory in the state of Florida and the USA's "electoral college" non-popular vote system.)
The 10% of Nader voters who voted honestly made a huge mistake by being honest, and they paid for it. But why should honestly voting for your favorite be a mistake? Couldn't there be a better voting system in which it is not a mistake? Meet Range Voting.