Mexico City (CNN) -- Hours before the end of Mexico's presidential campaign period Wednesday night, the ruling party's candidate made an unexpected proposal before a crowd of cheering supporters.
Josefina Vazquez Mota said she will invite current Mexican President Felipe Calderon to become the nation's attorney general if she wins Sunday's election.
The National Action Party (PAN) candidate is trailing in the polls and had appeared to be distancing herself from Calderon. Her campaign slogan is "Josefina Diferente."
But at a campaign rally in a Guadalajara stadium Wednesday night, she praised the "valor" of Calderon's fight against organized crime.
Calderon announced a crackdown on cartels shortly after taking office in December 2006. Since then, more than 47,500 people have died in drug-related violence nationwide, according to government statistics.
The comments from Vazquez Mota, who would be Mexico's first female president if she wins Sunday's vote, were a surprise twist at the end of an intense three-month campaign period.
Security and the drug war have been top issues for the four candidates vying for Mexico's presidency, who held their final campaign rallies Wednesday.
Mexican law prohibits candidates from campaigning during a four-day period starting Thursday. Voters will head to the polls in federal elections Sunday.
Numerous polls leading up to the elections have deemed Enrique Peña Nieto of the Institutional Revolutionary Party (PRI) the front-runner, giving him a double-digit lead over his closest competitor, Andres Manuel Lopez Obrador of the Democratic Revolution Party (PRD).
Peña Nieto closed his campaign with brief remarks in the northern industrial city of Monterrey on Wednesday night.
Earlier Wednesday, he led a rally on his home turf and party stronghold of Mexico state, where he was governor from 2005 to 2011.
"We are ahead in all the measurements, but this cannot in anyway allow us to be confident. On the contrary, this is the moment to redouble our efforts," he said to crowds of cheering supporters.
The front-runner summed up the proposals he has made during the past 90 days of campaigning, including stopping the rise in food prices, promoting an energy reform and giving social security to all Mexicans.
Meanwhile, supporters of leftist candidate Lopez Obrador packed the streets leading to Mexico City's central square.
Lopez Obrador was mayor of the capital city from 2000 to 2005, and the city is a stronghold for the PRD.
"Next Sunday there will only be two choices: more or less the same thing, or a true change," Lopez Obrador said, speaking before throngs of supporters in the same square that was packed with protesters after election authorities said he had narrowly lost the 2006 presidential vote to Felipe Calderon.
Lopez Obrador claimed election fraud and never conceded, referring to himself as "the legitimate president of Mexico."
"We are going to win the presidency again," the leftist candidate said Wednesday evening, pledging to focus on human rights and devote more attention to victims of violence.
Gabriel Quadri of the New Alliance, who trails far behind in the polls, spoke to supporters in the northern state of Zacatecas.
"Clearly we are going to win July 1," he said, pledging to push for structural reforms in the country, according to Mexico's state-run Notimex news agency.
More than 38% of voters surveyed prefer Peña Nieto, according to a poll from Consulta Mitofsky. That poll placed him 13 percentage points ahead of his closest competitor, Lopez Obrador.
Vazquez Mota ranks third with 20.8%, according to the polling firm. And Quadri had garnered support from less than 2% of voters.
Mexico's constitution bars the PAN's Calderon, who has governed the country since December 2006, from seeking a second term.
A victory for Peña Nieto would mark a triumphant return to power for the PRI, which controlled Mexico's presidency for more than 70 years, until the election of the PAN's Vicente Fox in 2000.
Criticisms of Peña Nieto and concerns about the PRI's possible return to power have fueled a student movement that has staged protests throughout the country in recent weeks.
CNNMexico.com's Tania L. Montalvo, Belen Zapata and Mauricio Torres contributed to this report.