The House-Senate vote difference
While there’s a lot of similarities in how Australians vote between the House and the Senate, they’ve never voted exactly the same. For a start, there are more options on the Senate ballot paper than the House ballot paper. Small parties will not run in all House seats (sometimes they run in very few) and thus can only attract Senate votes in many seats. This means the bigger parties have traditionally done better in the House, where they have less competition.