A political analyst says State Government Minister Terry Redman faces a huge challenge to hold his South West seat.
Mr Redman, who is a Nationals MP and the Minister for Agriculture, Forestry and Housing, won the seat of Blackwood-Stirling with a two-party preferred margin of nearly 25 per cent.
But, a redistribution which involved re-naming the seat Warren-Blackwood, has reduced that margin significantly.
Analyst Harry Phillips says Mr Redman is now in serious trouble after Labor decided to preference the Liberal candidate Ray Colyer ahead of him.
"Terry Redman is really going to have to struggle to win," he said.
"Because he's been a minister and high profile that will push up his vote, but he's also running against a candidate who is well known, Ray Colyer."
Mr Colyer is the Margaret River shire president.
Potential leadership vacuum
Mr Phillips says the WA Nationals are also facing a potential leadership vacuum.
He says the party's leader, Brendon Grylls, Mr Redman and Wendy Duncan face tough tasks to remain in the Parliament.
Mr Grylls has abandoned his safe seat of Central Wheatbelt to run for Pilbara, which has been a safe Labor seat.
Ms Duncan, who is standing in Kalgoorlie, and Mr Redman are both seen as possible leaders but they both face challenges to hold onto their seats.
Mr Phillips says losing Mr Grylls would be bad enough but losing Mr Redman would significantly add to the party's pain.
"He's a candidate for the leadership at any rate and if they were to lose two major forces in the ministry of a National Party label it would be a big setback for the party," he said.