Why did the Institutional Revolutionary Party (PRI), after 70 corrupt years in p

Why did the Institutional Revolutionary Party (PRI) after 70 corrupt years in power lose in 0 and can it make an effective comeback after winning power again in 2012? 4 pages long 3 sources from any legitimate mainstream book journal article periodical or newspaper (in that order of importance). No dictionaries or encyclopedias especially Wikipedia. cite a source using the APA Style for anything that is not common knowledge let alone if you quote from it. Use standard formatting (double-spaced 12-point Times or Times New Roman normal margins page numbering etc.). Do not do a Title Page or sub-headings. Do a Works Cites section (which will not count for length).