From Burton Kirkwood's The History of Mexico :
"In [the 1828] elections Manuel Gomez Pedraza [pictured left] ran as a conservative against former insurgent general Vicente Guerrero representing the federalist position. The election was so close that Guerrero protested the election results and "pronounced" against Gomez Pedraza. Backed by federalists and Santa Anna, Guerrero denounced the 1828 electoral vote. His actions established the precedent whereby elections would be held, but in actuality charismatic caudillos determined who would assume the office of presidency. As a result of Guerrero's opposition, the 1824 constitution existed only on paper."
For the latest on the the current Mexican presidential election fiasco, check out Mexico Elections and Lupa Ciudadana. My previous post on the subject is here.