CANBERRA, Australia — Prime Minister Malcolm Turnbull lost the support of key members of his party on Thursday and rivals emerged to challenge his leadership, grinding the House of Representatives to a halt, throwing the government into chaos and giving the revolving door of Australian politics another push.

Mr. Turnbull, a moderate former investment banker, has been under increased pressure to step aside since a dispute over a proposed energy plan to cut emissions resulted in a mutiny within his conservative Liberal Party earlier this week.

On Thursday, with Mr. Turnbull’s position in obvious jeopardy, two members of his cabinet said they would run in a party ballot expected to be held on Friday, and a third was also expected to do so. Such votes are held in secret and the rules are loosely defined, meaning that a dark horse candidate could yet emerge and win the leadership.

As of Thursday night, the candidates expected to run included:

• Peter Dutton, 47, a conservative who served as home affairs minister and narrowly failed to unseat the prime minister in a party vote on Tuesday.