The larger than expected field of 16 candidates includes two former NSW state MPs, former UBS investment bank boss and sacked NBN director Brad Orgill, and the secretary of the NSW Fire Brigade Employees' Union, Jim Casey.

Mr Casey is one of several  candidates from Senator Rhiannon's "eastern bloc" faction who were not expected to stand in the way of her bid for a further six-year stint in federal Parliament.

A senior Greens source said some within her own faction have lost patience with Senator Rhiannon, who will be into her 70s if she completes another term.

"Jim Casey is to the left of Chairman Mao. The only reason that he and half a dozen others from the eastern bloc are running against Lee is that they are pissed off that she is insisting on hanging on. You can't really blame them when people like Christine [Milne] and Bob [Brown] have called it a day and moved on," said the source.

In February 2001, Senator Rhiannon, who was then a member of the NSW upper house, delivered a speech in which she argued for limited terms to prevent careerist politicians becoming a feature of the party.

"The idea that an elected position should be rotated among members of an organisation rather than controlled by one individual for a long time has been one of the factors that attracts people to our movement and away from the old way of doing politics," she said.

At the time Ms Rhiannon was locked in a bid to convince former MLC Ian Cohen to retire.

Her then chief of staff, John Kaye, wrote a paper about preventing careerists dominating the ranks of the Greens. He recently began a second eight-year term in state Parliament.

Nominees from the hard left include James Ryan, Amanda Findley, Jane Oakley and Ben Hammond.

Cate Faerhrmann, who gave up her seat in state Parliament for an unsuccessful tilt at the Senate in 2013, has nominated. So too has former Australian Democrat MLC Arthur Chesterfield-Evans.

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