The difference is that RCV results in the "least worst" candidate winning. They receive the most #1 votes, but unless they achieve an outright majority, if they

The difference is that RCV results in the "least worst" candidate winning. They receive the most #1 votes, but unless they achieve an outright majority, if they only have a plurality then they only win by being the most preferred alternative vote by the voters. So the situation is that the leading parties have to spread their ideological base to incorporate more of the electorate. In addition, Australia has compulsory registration at 18 and compulsory voting (well, actually compulsory attendance at a voting location, the ballots are all secret). So the candidates have to appeal most to a plurality of their electorate, and they have to appeal least worse alternative to a majority.