Although Zardari has barely stirred out of the federal capital due to security concerns, his two rivals have been criss crossing the country to drum up support.

But the 53-year-old widower of former premier Benazir Bhutto, who became head of the PPP after she was assassinated in December last year, has been billed the front-runner to win the election despite the PML-N's decision to pull out of the ruling coalition and fielded a candidate against Zardari.

Sources said that Zardari expects to poll over 60 per cent of the 700 members in the electoral college, in an election necessitated by former President Pervez Musharraf's resignation on August 18.

PPP has been able to rope in the backing from smaller parties like the opposition Muttahida Qaumi Movement, Awami National Party and Jamiat Ulema-e-Islam and dissidents from the main opposition PML-Q.

The party commands adequate support in the two houses of parliament, the Senate and National Assembly, and the four provincial assemblies, which comprise the electoral college for the polls.

In significant pre-poll comments, Zardari has said that he intends to trim the President's sweeping powers, which included authority to dissolve Parliament and dismiss Premier.

He also vowed to defeat the "domestic Taliban insurgency" and said his country stands with the US in the fight in the war against terror.

Since the election schedule was announced last month, Zardari has largely been confined to the Prime Minister's House to which he shifted from his residence because of security concerns.

His rivals PML-Q secretary general Mushahid Hussain Sayed and former Chief Justice Saeed-uz-Zaman Siddiqui, who is backed by the PML-N, have travelled across the provinces to seek support for themselves.

Zardari met members of parliament and the provincial assemblies at the Prime Minister's House and Prime Minister Yousuf Raza Gilani travelled to provincial capitals to seek votes for him.

Most observers believe Siddiqui and Sayed stand no chance of winning against Zardari. Siddiqui has showed restraint and not issued any statement against his rival candidates but Sayed has openly targeted Zardari, raising questions about media reports on the state of his mental health and the source of USD 60 million in Swiss bank accounts that were recently unfrozen.

The PPP's leaders and ministers have mounted a spirited defence of Zardari and Gilani has said the premier and President should be from the same party to ensure stability.

Zardari's opponents, including Sharif, have also questioned the PPP's decision to field him without repealing the President's controversial powers to dissolve parliament and dismiss the Prime Minister.