We call it preferential voting and use it for our lower house (the Senate is a form of proportional called Single Transferrable Vote, also used in Ireland). Americans call it Instant Runoff.
Basically you number/rank the candidates and if nobody gets a majority of '1' votes, preferences are distributed by eliminating the least popular candidate and distributing by '2' and subsequent preferences, repeatedly until someone has a majority.
Within the bounds of single-member electorates it is strictly superior. Its huge advantage is that it eliminates the need for tactical voting and eliminates the issues with vote-splitting, so everyone just has to vote their honest order of preference, instead of guessing which "lesser evil" they think has the best chance of beating the "greater evil". It also ensures the candidate that wins is the most-preferred by 50%+1 in the electorate and would win any given two-way contest, hence why Americans call it Instant Runoff.