Mexicans go to the polls on 1 July to elect a successor to President Felipe Calderon. There are also elections for Congress and several state governors, as well as some local elections.
Who are the main presidential candidates?
Front-runner is Enrique Pena Nieto, 45, of the Institutional Revolutionary Party (PRI), which ruled the country from 1929 to 2000.
According to most opinion polls, the former governor of the State of Mexico has maintained a wide lead over his rivals. This suggests he has managed to shake off the PRI's past, which was tarnished by authoritarianism and corruption.
Andres Manuel Lopez Obrador is the candidate of the Party of the Democratic Revolution (PRD). Mr Lopez Obrador, 58, lost the 2006 presidential race by less than 1%.
He said there was widespread fraud in the 2006 vote, declared himself the "legitimate president" and called on his followers to occupy the streets.
Josefina Vazquez Mota, 51, is running on the governing National Action Party (PAN) ticket.
With the slogan "Different", she is trying to convince voters tired of the PAN's 12-year rule that she can reverse the country's sluggish economy and tackle heightened insecurity.
Gabriel Quadri de la Torre, 58, of the New Alliance Party (Panal) is trailing far behind.
His opponents have described him as a puppet of the powerful teachers union which, some say, has stifled reform of the education system.
What are the main issues?
Security and the poor performance of Latin America's second largest economy are the biggest worries for Mexican voters, according to pollster Mitofsky.
Mexico has achieved macroeconomic stability but has not redressed social inequality among its population.
All the presidential candidates have pledged to reduced poverty, which edged up from 44.5% to 46.2% between 2008 and 2010, according to the National Council for the Evaluation of Social Development Policy.
What about the drugs war?
The rampant drug-related violence in Mexico in recent years has barely surfaced on the campaign trail.
The approach that the three major candidates have mapped out has been criticised as vague and contradictory.
New proposals tend to focus on the reduction of drug-related killings.
Mr Pena Nieto has said his priority will not be arresting the drug lords, but reducing homicide, kidnapping and extortion by deploying large numbers of police and troops into places with the highest rates of violent crime.
Mr Lopez Obrador has pledged to change the current strategy, placing more emphasis on withdrawing the military from the streets, fighting corruption among government officials and reducing crime by tackling social inequality.
Ms Vazquez Mota wants to stick to President Calderon's policy and keep military forces at the forefront of the drug war.
She has pledged to pay more attention to the victims of drug violence, but has made it clear that she will never strike a deal with organised crime groups, as some have urged.
How significant have social media been in the campaign?
All the candidates have a strong presence on major social media websites.
The most visible is Mr Pena Nieto. However, his opponents, who include student protesters, have been waging fierce resistance online to his candidacy.
Ms Vazquez Mota has generated several Twitter trending topics, including when she urged women to withhold "cuchi cuchi", or hanky panky, for a month if their husbands do not vote.
According to Mr Lopez Obrador, his "movement to change Mexico" would have been "licked" were it not for social networks, which helped "break the siege laid by disinformation-disseminating media".
Experts are divided on the tangible influence of social media on the outcome of the vote. While some suggest social networks may sway undecided voters, which total around 20%, others point out that Mr Pena Nieto's lead is probably unassailable.
Mexico's internet coverage is low, with only 36% of the population online.
What are the student protests about?
A student movement "Yo soy 132" (I am 132) emerged after Mr Pena Nieto's team claimed that student hecklers had been planted by rival campaigns to sabotage his appearance at a private university.
A group of 131 young people posted a video on Youtube showing their student IDs. The clip went viral with many expressing a desire "to become the 132nd member" of the group.
Many of the students say a vote for Mr Pena Nieto would be a return to the past and criticise the media for portraying his victory as "a fait accompli".
What about the other elections taking place?
Voters will elect the 500 members of the Chamber of Deputies and 128 senators.
The make-up of Congress will have a significant bearing on the extent to which the new president can implement policies or reforms.
Elections for influential state governors are being held in Guanajuato, Jalisco, Morelos, Yucatan, Chiapas and Tabasco.
Political control could change in some of these states.
Mexico City is also electing a new mayor.
There are also elections for mayors and local congress in a number of states.
When does the president take office?
The new president will start a six-year term on 1 December. Mexican presidents are constitutionally barred from serving more than one term.
US jobs lost to trade deficit approx: 862,900
Mexico unemployment: 4.9%
35% of workers earn less than $10 a day
61.5% of workers earn less than $14 a day
Main export partners
US 73.5%, Canada 7.5% (2010)
Main exports to US
Assembled goods $16.3bn
Drug violence-related deaths:
2006-2011: 47,515 people
5,000 missing (CNDH)
Drug trafficking worth:
$10 -15bn annually
3rd largest producer after Afghanistan and Burma