mexico city tight general election loom next year mexican president enrique pena nieto face tough choice whether pursue graft probe involve prominent ally brazilian construction firm odebrecht mexico top prosecutor act attorney general alberto elias beltran friday fire federal attorney general responsible electoral crimes add fuel case may complicate president efforts shake allegations corruption run-up july 2018 presidential vote dismissal top electoral prosecutor santiago nieto come two days accuse emilio lozoya former boss state oil firm pemex longtime ally president pena nieto newspaper interview write ask declare innocent funnel odebrecht cash political campaign brazil odebrecht admit pay bribe several countries latin america include mexico president pena nieto party institutional revolutionary party pri dominant force mexican politics best part century long byword corruption mindful issue corruption become central 2018 election unpopular pri oversee arrest various former state governors lozoya pose difficult challenge give proximity president investigate lozoya deeply think would end party power stir public anger say paulo diez anti-corruption lawyer take government high-profile graft scandals four days become act attorney general alberto elias beltran dismiss santiago nieto ground break office code conduct public officials office say friday dismissal attack conservative national action party pan leftist party democratic revolution prd opposition party question impartiality pena nieto government santiago nieto tell newspaper reforma wednesday lozoya letter bid secure impunity odebrecht money enter political campaign nieto office confirm letter existence well investigation former pemex chief executive contact reuters lozoya say press conference innocent accusations funnel cash president pena nieto campaign president pena nieto also previously deny odebrecht bribe make way party coffers lozoya lawyer javier coello deny client write seek leniency interview coello also share reuters letter send santiago nieto lozoya ask inform criminal investigation call testify need letter mention appeal clemency odebrecht admit u.s. brazilian prosecutors pay 10.5 million bribe mexico detail payments make public though august brazilian mexican media report lozoya ask odebrecht executives bribe 2012 return contract cite testimony odebrecht employees monday week attorney general raul cervantes stand tell senators office conclude investigations odebrecht however detail yet publish graft probe mexico president 's ally pose tricky challenge ahead elections