Johor Baru Mentri Besar Datuk Seri Mohamed Khaled Nordin said Dr Mahathir has hijacked the opposition after the former premier was named as the coalition's choice for prime minister.
These were for Anwar to be given a pardon and made prime minister within a year of Pakatan winning the election, for PKR to be allocated the highest number of seats to contest the election and for Dr Mahathir to agree to institutional reforms.
The 22-year Mahathir era between 1981 and 2003 saw great development and economic growth.
With the country's most popular opposition leader Anwar Ibrahim now in jail on sodomy charges, the authoritarian who ran the country for two decades is seen as the biggest threat for current premier Najib Razak, who must call an election by August.
Former Malaysian prime minister Dr. Mahathir Mohamad, 92, will lead the Southeast Asian nation again if the opposition wins national elections due by August.
Pakatan Harapan secretary-general Saifuddin Abdullah said Anwar's wife Wan Azizah Wan Ismail is the alliance's candidate deputy prime minister.
"Dr Mahathir is sharp on policies and knows the workings of the government; Anwar will rally the urban crowd", said ISEAS-Yusof Ishak Institute fellow Norshahril Saat.
The Mahathir-led opposition, however, looks unlikely to unseat the ruling Barisan Nasional (BN) coalition, according to a survey conducted by independent polling firm Merdeka Center in December.More news: Thomas Monson, head of Mormon church, dies aged 90
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Mahathir, 92, was chosen on Sunday to lead the opposition after putting aside a decades-old feud with popular politician Anwar Ibrahim, who is now jailed on a conviction for sodomy.
Dr Mahathir and his former foe Mr Anwar have joined up in a bid to oust Mr Najib, with an election victory by the allied parties potentially paving the way for the incarcerated Anwar to eventually return and take over as prime minister.
"We are highly sceptical of the opposition's prospects if they continue to be split as things are now", Mr Ibrahim said.
Abdul Rahman Dahlan says it is no surprise that there are angry Pakatan Harapan supporters questioning why Dr Mahathir Mohamad and Anwar Ibrahim have forgiven each other so easily after trading insults over the past two decades.
Malaysia's political landscape has been shaped for almost two decades by a bitter feud between Anwar and Mahathir.
He can not run for political office for five years after his release unless he is pardoned by the King.
The opposition has often appeared disorganised and disunited - a far cry from the strong alliance that Anwar led at the 2013 polls - while the electoral system is strongly stacked in BN's favour, with the government long accused of gerrymandering.
Anwar's conviction and nine-year prison sentence that he received in 1999 were overturned in 2004 and he was released. "So let's, together with him, make it happen". In civil lawsuits, the US Justice Department has alleged that about US$4.5 billion was misappropriated from 1MDB. Mr Najib has denied the allegations.