Explainer: Vacancies filled in the Senate and the House of Representatives

Recently 2 casual vacancies have come up in the Australian Parliament. A casual vacancy is when a senator or member resigns or retires during their term.

Aug 24, 2020

Dr Mike Kelly, the Member for Eden-Monaro, resigned from the House of Representatives due to ill health and Senator Richard Di Natale retired to spend more time with his family.

Then there’s an election, right?

Casual vacancies in the House of Representatives usually trigger a by-election. In a by-election on 4 July, the people of Eden-Monaro chose Kristy McBain, the former Mayor of Bega, to replace Dr Kelly.

In the Senate, casual vacancies are filled when the parliament of that senator’s state chooses a replacement. The Victorian Parliament confirmed on 4 September that Senator Di Natale will be replaced by Lidia Thorpe.  Senator Thorpe will be the first Aboriginal person to represent Victoria in the Senate.

Can the State Parliament just choose whoever they want?

The replacement must be from the same political party as the senator who vacated the seat. This condition was convention—tradition— until 1977. At the 1977 referendum the people of Australia voted to include this condition in the Australian Constitution.

Why don’t they have elections to replace senators like they do for members of the House of Representatives?

The Australian Constitution contains a number of ways in which the Senate and House of Representatives are different, and this is one of those ways.

In the House of Representatives a by-election follows a similar process to a general election, but only in a single electorate. In both cases a candidate must receive a majority vote from the people in their electorate.

However, at a general election senators are elected by achieving a quota of votes, not a majority vote. The quota of votes is determined by the number of vacancies which need to be filled. If an election was held for an individual Senate seat, it would mean the candidate would require a different number of votes from all the other senators of that state or territory, which would be inconsistent and unfair.