By Dave Graham MEXICO CITY (Reuters) – Accused a generation ago of engineering the "perfect dictatorship," Mexico's ruling party is now close to agreeing on a plan that could weaken the presidency and strengthen Congress in order to win votes for a major energy reform. The Institutional Revolutionary Party (PRI) and its opposition rivals are shortly expected to unveil the blueprint for a reform aimed at giving Congress greater oversight of government and allowing lawmakers to serve consecutive terms. Billed as a step forward for democracy, the electoral reform is a bargaining chip for President Enrique Pena Nieto's most ambitious plan – changing the constitution to allow more private capital into the state-controlled oil industry. The energy bill is the central pivot of a broader drive for change from telecoms to education that Pena Nieto hopes will help boost Mexico's economic growth, which has long lagged that of other countries in the region.