Muhyiddin Yassin, 73
The seasoned politician has spent over four decades as an elected representative, with extensive stints as Johor chief minister and Cabinet minister, most of them with his former party Umno.
Tan Sri Muhyiddin succeeded Tun Dr Mahathir Mohamad as premier in March after leading Parti Pribumi Bersatu Malaysia to defect from Pakatan Harapan. His Perikatan Nasional (PN) pact governs with a slim majority, and his attempt at forestalling a vote in Parliament by proposing emergency powers was rebuffed by the King, Sultan Abdullah Ahmad Shah. His PN allies stand behind him for now, but unhappiness festers in Umno, the largest party in the pact.
Najib Razak, 67
Former prime minister
Najib, former president of Umno, was prime minister from 2009 to 2018.
His leadership ended in loss, when Umno was defeated in the 2018 General Election under the weight of the 1Malaysia Development Berhad scandal.
He is now appealing against a 12-year sentence for graft linked to the state investment fund, and remains an influential figure in the party.
However, his recent push for Umno to ditch Mr Muhyiddin in favour of Opposition Leader Anwar Ibrahim has lost him some support among the party faithful.
Mahathir Mohamad, 95
Former prime minister
Tun Dr Mahathir has twice served as the country's prime minister, most recently at the helm of Pakatan Harapan (PH). He refused to join Mr Muhyiddin in leaving PH in March, and resigned as premier.
He remains a father figure statesman whose opinion and influence are widely sought.
Dr Mahathir has repeatedly called for a vote of no confidence to be held in Parliament to determine if Mr Muhyiddin still commands majority support.
Anwar Ibrahim, 73
Datuk Seri Anwar has eyed the premiership for over two decades since being sacked as deputy premier by Dr Mahathir in 1998.
Last month, he claimed to have a "strong, convincing, formidable majority" to form a new government and that the Muhyiddin administration has "collapsed". But despite gaining a royal audience on Oct 13, he has failed to prove his claim.
Ahmad Zahid Hamidi, 67
Zahid took over the reins at Umno when Najib quit the presidency.
Zahid is also tied up in dozens of graft charges, and remains outside Mr Muhyiddin's Cabinet.
Umno and Mr Muhyiddin's Bersatu have been at loggerheads over primacy in the ruling pact, and Zahid has threatened to withdraw Umno's support.
But an Umno Supreme Council meeting on Monday chaired by Zahid decided to continue backing PN.
Azmin Ali, 56
Senior Minister for the Economy
Once Mr Anwar's closest lieutenant, he became one of Dr Mahathir's most trusted ministers after PH's victory in 2018.
He was a crucial architect of the move to block Mr Anwar from becoming prime minister during PH's rule, which led the PH government to collapse in February. One of Mr Muhyiddin's most trusted allies, he is seen as a key proponent of last week's ill-fated request for emergency powers.
Hamzah Zainudin, 63
Home Affairs Minister
The Bersatu secretary-general was a junior minister in Umno until its election defeat in 2018, after which he defected to Bersatu.
He, too, helped to block Mr Anwar's ascent to the top job in February. As the minister in charge of security, he was a key player in the bid to declare an emergency.