By Noe Torres
ECATEPEC, Mexico (Reuters) - Mexicans voted for new governors in three states on Sunday in races slated to be big wins for the main opposition party and a blow to President Felipe Calderon ahead of next year's presidential election.
The key ballot is in the populous State of Mexico, where the vote is seen as a popularity test for the outgoing governor, Enrique Pena Nieto, an early favorite to win back the presidency for the Institutional Revolutionary Party, or PRI.
The PRI hopes the telegenic Pena Nieto, 44, will be a fresh face for the party whose 70-year rule was dogged by accusations of vote-rigging and corruption before losing power in 2000.
Pena Nieto backs the PRI's gubernatorial candidate, Eruviel Avila, the popular former mayor of the state's largest municipality Ecatepec, where voters turned out despite heavy rains from Tropical Storm Arlene that flooded neighborhoods and closed down streets.
Polls show Avila far ahead of the candidates running for Calderon's conservative National Action Party, or PAN, and the leftist Party of the Democratic Revolution, PRD.
"The PAN or the PRD has never come here to help, Eruviel is the only one who has been giving us a hand," 58-year-old housewife Maricarmen Trejo said as she headed to the polls.
The PRI never lost power in the State of Mexico, a bastion of old-style machine politics where opponents accuse the government of using public funds to sway voters.
Opinion polls show the PRI also likely to sweep gubernatorial races in the states of Coahuila and Nayarit, further bolstering its platform for a comeback after a decade on the sidelines during two consecutive PAN governments.
Both states have seen a dramatic rise in drug killings over the past year, a critical liability for Calderon who has staked his term on fighting powerful cartels since taking office in late 2006. With drug violence surging over the past four years -- more than 40,000 deaths to date -- some voters are fed up.
"The violence is always getting closer, you see it touching your family, your neighbors," Israel Segura, 33, a vendor in Ecatepec said.
DRUG MONEY IN CAMPAIGNS
National protests over the past few weeks, led by a crusading poet whose son was killed by drug gangs, has turned up the pressure on Calderon to respond to victims complaints. Security for the first time is overtaking the economy as voters' top concern.
Worries about drug cartels backing candidates are swirling as the country gears up for the 2012 election.
In a rare admission by a politician, former PAN cabinet member Xochitl Galvez told the El Universal daily that she had been offered large sums of money by a cartel while running for governor of the central state of Hidalgo last year.
She did not win the race and said she refused the cash offer but did not say anything at the time out of fear.
"The offer was very clear," Galvez told the newspaper.
A messenger from the drug cartel said, "'I have instructions to give you 50 million pesos ($4.3 million), you are several points down with only a few weeks until the elections. With that money you can pay off all the leaders (so they support you.)'"
Hidalgo is also set to elect 84 new mayors on Sunday.
(Additional reporting by Mica Rosenberg; Writing by Mica Rosenberg; Editing by Paul Simao)