The meeting of Malaysia's largest political party is around the corner.

In the past, Umno general assemblies could determine the country's political trajectory.

During the 1998 assembly, a book entitled 50 Dalil Kenapa Anwar Ibrahim Tidak Boleh Jadi PM (50 Reasons Why Anwar Ibrahim Cannot Become Prime Minister) was circulated among delegates. In the following year, tensions between then Prime Minister Mahathir Mohamad and Anwar surfaced, and the latter was sacked as deputy prime minister for sexual misconduct and corruption.

At the 2002 assembly, Tun Dr Mahathir surprised pa rty delegates by resigning as Umno president. He retracted his resignation within an hour, but retired the following year and handed over power to Tun Abdullah Badawi.

At the 2005 meeting, Youth chief Hishammuddin Hussein waved the Malay keris, which was seen as an act of provocation towards non-Malays. Since then, Malaysia has witnessed ethnic tension which culminated in the party's poor showing in the 2008 elections.

However, at this year's assembly, we would not expect such drama. Prime Minister and party president Najib Razak has taken steps to control all proceedings and how information will be disseminated to the public. Unfortunately, such controls could potentially invite negative speculation on the leader, as he continues to face questions over the 1 Malaysia Development Berhad (1MDB) saga and RM2.6 billion (S$861 million) donations in his bank accounts.

This year's Umno general assembly, to be held from Dec 8 to 12, is significant for several reasons. First, the public expects the Prime Minister to answer questions regarding the 1MDB saga. Even though he may not use this platform to respond to criticisms, many would expect him to remind the public to avoid any speculation, as investigations are ongoing.

Second, this year's assembly showcases a new Umno leadership. This is the first Umno assembly since the removal of Tan Sri Muhyiddin Yassin and Datuk Seri Mohd Shafie Apdal from the Cabinet. Ironically, Mr Muhyiddin and Mr Shafie continue to hold leadership positions in the party as deputy president and vice-president respectively.

Third, this assembly is a test of Dr Mahathir's influence in the party. Dr Mahathir has been campaigning for the Prime Minister to resign. Past experience shows that Dr Mahathir will not relent until his agenda is fulfilled. In 2008, he quit the party, pressuring then Prime Minister Abdullah to step down. But this time, Dr Mahathir's strategy is different. He continues to be a party member, and prefers to speak to disgruntled Umno members, lobbying them to pressure Mr Najib to resign.

Umno leaders and Dr Mahathir have crossed swords even before the assembly started. Supreme Council member Tajuddin Abdul Rahman opined that Dr Mahathir should not turn up for the assembly because he attended the Bersih 4.0 (Coalition for Clean and Fair Elections) rally in August this year.

Meanwhile, Dr Mahathir claimed this month's meeting is futile because the 1MDB issue and RM2.6 billion in Mr Najib's accounts will not be raised. Still, he insisted he will attend the assembly because he is an Umno member and has received an invitation letter.

With the general election coming in a couple of years, Mr Najib should use this year's assembly to shore up support for the party. Some analysts mention that support within the party for the embattled leader remains strong. The way he carried himself during the recent visits by US President Barack Obama, Chinese Prime Minister Le Keqiang and India's Prime Minister Narendra Modi has won admirers among Malaysians. His hard-handedness in tackling terrorism has also won praise by the international community.

However, some measures undertaken by the party could potentially undermine his credibility. Unheard of in Umno's recent history: Mr Muhyiddin is not allowed to officiate the Youth, Women, and Women's Youth wing assemblies. Is Umno afraid he will use such platforms to revolt against the Prime Minister?

Moreover, the Umno assembly will be held mostly behind closed doors and media reporting will be restricted. Umno secretary-general Tengku Adnan Tengku Mansor said this is to prevent the media from spinning information. This move again raises speculation that Umno is trying to control information. Such measures will likely raise questions about whether Mr Najib is afraid to confront his critics or that he has something to hide.

The crux of the matter is that Mr Najib must unite the party and regain support from disgruntled members. Failing which, Umno may split just like Parti Islam SeMalaysia, which saw the progressive faction breaking away from the conservatives in this year's muktamar (congress).

Mr Najib should use this assembly to make amends with Mr Muhyiddin and Dr Mahathir. Umno unity is crucial for the Prime Minister before he can even think of strengthening the National Front coalition, which is also fragmented internally. But first, he needs to dispel perceptions that he is afraid to confront critics.

• The writer is a Fellow with the Iseas-Yusof Ishak Institute. He does research work on Singapore, Malaysian and Indonesian politics.