The Commonwealth Electoral Act 1918 is an Act of the Australian Parliament which continues to be the core legislation governing the conduct of elections in Australia, having been amended on numerous occasions since 1918. The Act was introduced by the Nationalist Party of Billy Hughes, the main purpose of which was to replace first-past-the-post voting with instant-runoff voting ("preferential voting") for the House of Representatives and the Senate. The Labor Party opposed the introduction of preferential voting. The Act has been amended on several occasions since.