ONE of Nicola Sturgeon's key ministers is fighting to save her political career amid a furious scramble within the SNP to become candidates in next year's Holyrood election.

Maureen Watt, the minister for public health, faces being ousted from her seat by regional MSP Christian Allard, who is bidding to stand in the Aberdeen constituency she won from the Lib Dems in 2011.

Sitting MSPs are rarely challenged and battles between established Holyrood figures are almost unheard of.

But the contest to become the Nationalist candidate in Aberdeen South and North Kincardine is just the latest in a series of fierce struggles as senior party figures try to secure a constituency to fight next May.

Humza Yousaf, the Europe minister, is locked in a battle to stand in Glasgow Pollok, while no fewer than nine hopefuls are seeking selection to stand in neighbouring Glasgow Provan.

Another regional MSP, Chic Brodie, recently failed in a bid to be selected to fight the Ayr constituency, losing out to Glasgow councillor Jennifer Dunn.

Two sitting MSPs have already been deselected during the wave of infighting.

Edinburgh Western MSP Colin Keir was rejected by his local party in favour of his former parliamentary aide Tony Giugliano and Nigel Don was edged aside in Angus South in a process branded "brutal" by fellow MSP Christine Grahame.

The scramble for seats is a sign of the SNP's soaring success in the polls, which suggest Ms Sturgeon's party is on course to win all but a tiny handful of Holyrood's 73 constituencies.

However, under Holyrood's proportional system, the predicted size of the SNP vote would also make it impossible for the party to win many of the remaining 56 regional seats.

According to the most recent survey only the top candidate on the SNP list in each region could be confident of being elected.

Sources said French-born Mr Allard, a popular figure at Holyrood, decided to seek the nomination in Aberdeen South and North Kincardine after he was blocked from standing in the Aberdeenshire East seat due to be vacated by Alex Salmond by the imposition of an all-women shortlist.

His decision has forced Ms Watt, a former schools minister, into an unwanted battle.

In a mini-manifesto for local members, she lists "taking the oath in Doric," when she first entered Holyrood in 2006, as one of her main achievements.

She has won endorsements from a number of MSPs, MPs and local councillors.

The contest has been given an added edge because Ms Watt's son, Stuart Donaldson, worked as an aide to Mr Allard before he won the West Aberdeenshire and Kincardine Westminster seat in the General Election.

A source said: "Christian thought he was a shoo-in for Alex Salmond's seat and was not happy when an all-women shortlist was imposed.

"Some people in the party questioned the use of all-women shortlists with scenarios like this in mind."

In Glasgow Pollok, the seat held by former Scottish Labour leader Johann Lamont, Mr Yousaf is campaigning hard against John Flanagan, a former Labour councillor turned lawyer.

The long queue of hopefuls to stand in Glasgow Provan, currently held by Labour's Paul Martin, is headed by Duncan Ross, a respected stalwart who served as SNP national secretary, and Ivan McKee, who rose to prominence with the Business for Scotland Yes campaign group.

Another SNP source said: "There are some interesting selection battles taking place and it is certainly unusual to challenge a sitting MSP but it also a recognition of the ambition within the party."

Neither Ms Watt nor Mr Allard returned calls from The Herald.