Former speaker Bronwyn Bishop is facing a Melbourne Cup field of contenders for her Sydney seat of Mackellar.

Ms Bishop will face at least eight challengers, including Walter Villatora, who was campaign manager for former prime minister Tony Abbott, and businessman Bill Calcraft.

Jason Falinski, who works in the office of the state's Transport Minister Andrew Constance, is also making a tilt for preselection.

Julian Leeser remains the favourite to win preselection in Philip Ruddock's seat of Berowra.

Meanwhile the Prime Minister's attempts to protect the Member for Hume, Angus Taylor, has been successful — he is facing no challengers.

Macarthur MP Russell Matheson was contemplating a move across to Hume to challenge Mr Taylor, but decided against it after Mr Turnbull urged him to stay put and fight for his marginal seat.

But Hughes MP Craig Kelly could still be facing a fight, despite similar efforts from Mr Turnbull to shore up his position.

Sutherland Shire councillor Kent Johns has pulled out of the race.

But another local Liberal Michael Medway, who ran for the Coalition against former opposition leader Mark Latham in Werriwa in 2004, has still put his name forward for preselection.

Mr Abbott has also renominated for his Sydney seat of Warringah, and former frontbencher Bob Baldwin has decided he will recontest his seat of Paterson, which is nominally Labor after the most recent redistribution.

He may face a challenge from veteran Labor frontbencher Joel Fitzgibbon, whose seat was effectively abolished in the same redistribution.

Some MPs have been speculating that Labor MP Jill Hall may retire from her nearby seat of Shortland, allowing Charlton MP Pat Conroy to contest her seat, and Mr Fitzgibbon to run in the former seat of Charlton, which is to be renamed Hunter.

But Ms Hall maintains she has not yet made up her mind about her future, irritating some in the ALP who had hoped the issue would be resolved by now.

Meanwhile, maverick Liberal senator Bill Heffernan has decided to bow out of politics.

The colourful New South Wales senator was up for re-election at the next poll, but has confirmed he would not be standing.