Mexico's third-place presidential candidate is joining in allegations that weekend elections were marred by campaign spending violations and inequities that had a decisive effect on the vote.

Even though the violations won't overturn the election results, National Action Party candidate Josefina Vazquez Mota said, they should force changes in electoral laws for future votes.

Vazquez Mota joined Andres Manuel Lopez Obrador of the leftist Democratic Revolution Party in complaining of excessive spending by apparent winner Enrique Pena Nieto of the Institutional Revolutionary Party (PRI) prior to Sunday's elections.

Vazquez Mota also complained Thursday about pre-election polls that put Pena Nieto ahead by double digits, while preliminary vote counts indicate he won by about six points. She calls the erroneous polls "propaganda."

The PRI ruled for 71 years as a single party known for coercion and corruption, but also for building Mexico's institutions and social services. It was often accused of stealing elections, most infamously the 1988 presidential vote.

However, PRI governments were also known for keeping a lid on organized crime, whose battles with government and each other under former president Felipe Calderon have taken more than 50,000 lives and traumatized the country.