Ghana\'s ruling party was Saturday due to stage an unprecedented presidential primary with the wife of ex-leader Jerry Rawlings challenging incumbent John Atta Mills for the nomination. The primary at the National Democratic Congress (NDC) convention is between Atta Mills and Nana Konadu Agyemang Rawlings, wife of the ex-military ruler who later became an elected president. The convention, originally scheduled to begin at 1000 GMT, was being delayed to enable all delegates to attend, NDC spokesman told AFP at the venue. \"We are waiting for ... the arrival of leaders from the regions to start the programme. The candidates are all around and waiting to be ushered into the meeting venue,\" James Asante said. Wearing white, Rawlings, a mother of four, arrived at the venue accompanied by her husband and staunch supporter, also in white. While Ghana has been seen as a rare example of stable democracy in west Africa in recent years, Saturday\'s primary is the first time in the country\'s history that a sitting president will have to compete for his own party\'s nomination. Much will be at stake in the December 2012 presidential vote, with Ghana having recently joined the ranks of the world\'s large-scale oil producers and seeking to steadily increase output -- along with resulting revenue. Jerry Rawlings, who maintains wide influence in Ghana, seized power in successive coups in 1979 and 1981 before serving as the elected president from 1993-2001. Some 3,000 delegates are expected at the primary held in the city of Sunyani in the Brong-Ahafo western region of Ghana, the country chosen by Barack Obama for his first visit to sub-Saharan Africa as US president in 2009. Analysts said that while Rawling\'s wife is counting on her husband\'s popularity, she is not likely to have an easy ride. Her campaign has been boosted by the strong support of her husband, a ruling party founder and major critic of the Atta Mills administration. When her husband was in power, she founded and ran the \"31st December Women Movement,\" a non-governmental organisation for women\'s empowerment, where hundreds of women underwent various kinds of technical training. The couple accuse the current administration of failing to prosecute officials from the previous government for alleged corruption. Rawlings says she is in the contest to restore hope and dignity to ordinary Ghanaians. Atta Mills narrowly won the vote in 2008 with a less than one percent margin against a candidate from the party of incumbent John Kufuor, widely respected for having bowed out gracefully following his two terms in office.