Constitution of Australia
The convention that, when the Senator from a particular State vacates his or her position during the term of office, the State government concerned would nominate a replacement from the same political party as the departing Senator. This convention was allegedly broken first by the Lewis government of New South Wales and then by the Bjelke-Petersen government of Queensland, who both filled Labor vacancies with, respectively, an independent and a Labor member opposed to the Whitlam government.