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KUALA LUMPUR, Jan 7 (Reuters) - Malaysia's opposition alliance named former premier Mahathir Mohamad on Sunday as its prime ministerial candidate for a general election this year, although the authoritarian who ran the country for two decades and is now 92 years old faces an uphill task.
With the country's most popular opposition leader Anwar Ibrahim in jail, Mahathir is seen as the biggest threat for premier Najib Razak, who must call an election by August but is engulfed in a corruption scandal.
Still, an independent survey showed the opposition would have difficulty beating Najib, due to divisions within its own camp and unfavourable electoral boundary changes.
Mahathir and former foe Anwar have joined up to oust Najib, and an election victory by their alliance could also potentially pave the way for Anwar to return and take over as prime minister.
If the opposition wins, it would immediately start the process to obtain a royal pardon for Anwar so that he can be eligible to become prime minister, secretary general Saifuddin Abdullah said at the alliance's convention.
Anwar's wife Wan Azizah Wan Ismail will be the coalition's candidate for deputy prime minister.
Mahathir, who during his 22-year tenure as prime minister earned a reputation of being a no-nonsense authoritarian with little time for dissenters promoting liberal values, stands to become the world's oldest leader if the opposition wins.
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.
The survey showed that although BN's share of the popular vote will shrink further, it can potentially regain a two-thirds majority in parliament, The Malaysian Insight reported on Sunday.
Merdeka Centre's director Ibrahim Suffian said the Mahathir-led group was at a disadvantage due to a split in the opposition and the redrawing of electoral boundaries that critics say favour the ruling government.
The Pan-Malaysian Islamic Party (PAS), which was part of the opposition group in 2013, is no longer part of the pact.
"We are highly sceptical of the opposition's prospects if they continue to be split as things are now," Ibrahim said.
Malaysia's political landscape has been shaped for nearly two decades by a bitter feud between Anwar and Mahathir.
Anwar was once a protege of Mahathir, and the rising star of Malaysian politics, but they had a falling out in the late 1990s. Anwar was jailed on charges of sodomy and graft, after being sacked as the deputy prime minister. He denied the charges, dismissing them as politically motivated.
Anwar later led an opposition alliance to stunning electoral gains in 2013. Najib's coalition lost the popular vote in that election, but won a majority of the seats in parliament.
Anwar was convicted and jailed again in 2013 for sodomy, a charge he says is an attempt to end his career.
The sodomy conviction disqualifies Anwar from political office and from contesting the next election. A royal pardon, however, would let him contest.
Opposition to Najib has brought Anwar and Mahathir back together.
Najib has been embroiled in a corruption scandal involving state fund 1Malaysia Development Berhad (1MDB). In civil lawsuits, the U.S. Justice Department has alleged that about $4.5 billion was misappropriated from 1MDB.
The fund has denied any wrongdoing and Najib, who founded 1MDB, has denied all allegations of corruption against him and was cleared of wrongdoing by Malaysia's attorney-general. (Reporting by Liz Lee, writing by A. Ananthalakshmi; Editing by Himani Sarkar and Susan Fenton)