Gillani was declared as the candidate of PPP on the eve of closing of nominations for the Prime Ministerial elections by PPP spokesman Farhatullah Babar who read out a brief statement saying he had an enormous responsibility to lead the coalition. He is currently PPP's vice-chairman.
After the national assembly holds the formal elections on March 24, the new Prime Minister is set to be sworn into office by Musharraf the next day.
The election of Gillani, who spent four years in prison over allegations that he abused his authority as a Speaker, is a certainty given the majority the incoming PPP-Pakistan Muslim League-N coalition has in Parliament.
The candidature of Gilliani, who defeated former Prime Minister Nawaz Sharif in 1988, is likely to further expose the serious differences within PPP since veteran politician Makhdoom Amin Fahim, another close Bhutto aide, was the initial front runner.