Is that without a runoff they inevitably take votes away from the candidate that voter would consider the lesser of two evils. e.g. I might prefer a libertarian, or a very staunch conservative, but I'm going to vote for a moderate R over a D, so by voting for the L instead of the R, without a runoff, I am literally tossing that vote in the garbage as nothing more than a protest vote. I'd rather get 50% than 0% of what I want, and I know 100% can't happen anyway since for instance I really doubt anyone would like my idea of freezing all our dead unless they opt out. Haven't seen any candidates proposing multi-billion dollar vaults for storing millions of human Popsicles. Somewhere between 1-99% there's a cutoff for everyone about 'good enough' and protest vote, but in a runoff you can legitimately cast that vote without burning yourself and you'd see a lot more of them cast for 3rd party and I think before long you'd get enough in a runoff system to allow things besides R & D.