BUKIT MERTAJAM (THE STAR/ASIA NEWS NETWORK) - Polls for the Permatang Pauh parliamentary by-election opened at 8am on Thursday with voters lining up from very early to cast their ballots.

The by-election sees a four-cornered fight between Barisan Nasional's Suhaimi Sabdin, Parti Keadilan Rakyat (PKR) president Datuk Seri Dr Wan Azizah Wan Ismail, Azman Shah Othman from Parti Rakyat Malaysia (PRM) and independent Salleh Ishak.

The Permatang Pauh seat fell vacant after opposition leader Datuk Seri Anwar Ibrahim, who is serving a five-year jail sentence for sodomy, lost his eligibility as a Member of Parliament when the Pardons Board rejected his appeal against his conviction.

Anwar, who is PKR adviser, won the seat by a majority of 11,721 votes in the May 2013 general election. He polled 37,090 votes to Barisan's Mazlan Ismail who had 25,369 votes.

This is Dr Wan Azizah's second bid for the seat and the second by-election in Permatang Pauh in seven years. In 2008, about six months after winning the seat for a third term, a by-election was called when Dr Wan Azizah resigned to enable Anwar to make a return to Parliament.

The PKR president is the favourite to win after a campaign riding on the unpopular GST policy as well as former leader Tun Dr Mahathir Mohamad's tirade against Prime MInister Najib Razak.

Permatang Pauh is a Malay-dominant seat where Malays make up 70 per cent of the voters, Chinese comprise 23 per cent and Indians and others 7 per cent.

Her party still enjoys strong Chinese support while Umno holds sway over the Malay voters. The Indian vote is said to be "very fluid".