The formation of Pakatan Harapan (PH), Malaysia's new opposition alliance, doesn't quite close the circle for the key opposition parties after two years of antagonism between them.

In a country where stability within political alliances is a prime prerequisite for electability, the replacement for the old opposition caucus Pakatan Rakyat (PR), which unravelled last month, allows anti-government voters to put a name to their hopes of ending the long-time rule of the Barisan Nasional (BN) coalition. Indeed, Harapan is Malay for "hope".

But there are issues PH must resolve before the next general election, which must be called by 2018. Chief of these is the residual animus between the members of PH, launched on Tuesday, and erstwhile PR partner Parti Islam SeMalaysia (PAS).

PR had imploded over arguments in the selection of the chief minister of Selangor state, and even whether opposition leader Anwar Ibrahim was its clear prime ministerial candidate. But the key rift was over hudud - the draconian Islamic criminal code - that PAS wants to implement. This is opposed by PR partner Democratic Action Party (DAP).

Now a splinter party of PAS, Parti Amanah Negara, made up of rebels of the Islamic party who were sidelined in the June party polls, has combined with DAP and Anwar's Parti Keadilan Rakyat (PKR) to form PH. Amanah has endorsed Anwar - now serving a jail term for sodomy - as the man for the top job should PH win the next general election.

But having PAS outside the new opposition caucus is problematic - even with it in the old alliance there were squabbles over seats leading to three-cornered fights that benefited only BN. PAS is labelling Amanah members as "traitors" and will be loath to give them a free pass in wards that have traditionally been reserved for the Islamic party.

BN's linchpin Umno, which clearly fomented dissent within PR, will be glad that PAS - its main rival for the crucial Malay vote - continues to be at loggerheads with the rest of the opposition.