Mr Rudd and his wife Therese Rein urged voters yesterday to contact the 103 MPs and senators who make up the labor caucus to let them know their preferred candidate for prime minister.

Other countries have adopted measures which give voters opportunities to have a greater influence over who is selected as the nation's chief executive. The most obvious is the United States elected executive presidency, but less radical approaches exist.

Israel briefly experimented with what University of Sydney academic Gil Merom described as a ''quasi US presidency'' by allowing voters to directly elect the prime minister.

But Dr Merom that there was no guarantee a directly elected prime minister could get his or her agenda through parliament and Israel reverted to a more traditional parliamentary system.

''Once a prime minister is selected separately, it turned out he is ever more dependent on small parties. So they reverted back,'' he said.

Other reform options would give members or supporters of political parties a say on their parties' parliamentary leaders, as occurs in Britain and Canada.

Rank-and-file members of the British Labour and Conservative parties vote on the party leadership.

University of Adelaide political scientist Professor Clement Macintyre said the systems used by the British parties made it difficult for MPs to bring on swift leadership challenges similar to the one used to depose Mr Rudd in 2010. ''You can't have that sudden death experience,'' Professor Macintyre said.

''I don't doubt that the so-called faceless men would have operated in a very different way if they had known that the best they could do is provoke a spill motion that would play out over 10 weeks.

''Backbenchers would become a bit more interested in popular opinion.''

Direct election of leaders by the party-rank-and-file failed to prevent the Australian Democrats from suffering repeated leadership crises and then electoral oblivion.

Professor Macintyre said there was no guarantee that MPs could work with a leader who had been selected by their party's supporters or branch members.

''If it was a rank-and-file election at the moment I'd be less confident Julia Gillard would win it than I am of [her] winning from the caucus,'' he said.

''How would Labor be if the rank-and-file installed Mr Rudd as Labor and the parliamentary party said, 'can't work with him'?''

ANU Emeritus Professor and republican activist John Warhurst said high levels of public support for a directly elected presidency model for an Australian republic demonstrated that many people wanted greater involvement in choosing their leaders.

''There's a sense in the community I think that they want involvement,'' Professor Warhurst said. ''The younger generation are brought up on voting in Australian Idol and all these sorts of things, and it flows on to attitudes towards the political system.''