Mexico City - Mexican President Felipe Calderon was dealt a massive blow in midterm legislative elections, which are widely considered to be a major test for the
2012 presidential poll.

The Revolutionary Institutional Party (PRI) wrested control of the lower house of the Mexican Congress from Calderon's National Action Party (PAN), according to preliminary results.

Many had little hope in the PRI after it lost power in 2000, after 71 years. But on Monday, the daily El Universal proclaimed on its front page: "The PRI returns."

Conservative Calderon, in power since 2006 after defeating the centre-left Andres Manuel Lopez Obrador by just 0.58 percentage points, cannot stand for re-election himself. But Sunday's result confirmed that he will have trouble pushing through his favoured measures in the second half of his mandate.

The PRI also won at least four of the weekend's six elections for governor. The party held its ground in Nuevo Leon, Campeche and Colima, and also won in the state of Queretaro, which was a PAN stronghold. The PRI was also claiming victory in San Luis Potosi, though no clear results were yet available there.

The PAN only won in Sonora, a state in which a fire last month at a day care centre claimed the lives of 48 children. With the tragedy fresh in mind, the state's voters turned away from the ruling PRI.

The PAN had campaigned aggressively against the PRI and called on voters to validate at the polls the fight against drug traffickers launched by Calderon since his inauguration, with thousands of soldiers and federal police officers deployed across the country.

Mexicans showed their president that they remain worried about the recession and increasing violence, and they are also growing wary of politicians.

The campaign by some civic groups asking people to annul the vote - a gesture of rejecting politics in a country with compulsory adult suffrage - had some effect, with 6.5 per cent of the ballots being void, which was well above the usual percentage.

"We must be sensitive and heed the call made to us by those who decided not to vote or not to support a party today," Calderon said in a televised address.

The PAN still has no strong candidate for the 2012 presidential election, after holding the presidency for two consecutive terms. The PRI has for three years fielded Mexico state Governor Enrique Pena Nieto, who emerged as the winner of the midterm election.(dpa)