Although the House of Commons does not formally elect the prime minister, by convention and in practice, the prime minister is answerable to the House, and therefore must maintain its support. In this way, the position of the parties in the House is of overriding importance. Thus, whenever the office of prime minister falls vacant, the monarch appoints the person who has the support of the house, or who is most likely to command the support of the housenormally the leader of the largest party in the housewhile the leader of the second-largest party becomes the leader of the Opposition. Since 1963, by convention, the prime minister has always been a member of the House of Commons, rather than the House of Lords.