Mexican President Vicente Fox, whose term has been stymied by Congress, faced an even larger legislative opposition on Monday, one day after his conservative party took a beating in mid-term polls.
Early results show Fox's National Action Party (PAN) losing key seats in the 500-seat Chamber of Deputies as well as important governorships.
The Institutional Revolutionary Party (PRI), which ruled the country for 71 years before Fox became president in 2000, won four of six state governorships in play Sunday and increased their majority in Congress.
The center-left Party of the Democratic Revolution (PRD) also performed well, nearly doubling its representation in the lower chamber to around 100 seats and sweeping local elections in Mexico City, the world's most populous city with 22 million people.
PRD leader and Mexico City Mayor Andres Lopez Obrador is the country's most popular politician and tipped as a future presidential candidate.
Final election results will be released later today. As it stands Fox's party will have between 148 and 158 seats in the lower chamber of congress, while the PRI will have between 222 and 227 seats.
Fox, who saw his ambitious reform agenda thwarted in Congress during his first three years in office, put on a brave face after the results starting trickling in.
The election, held halfway through his six-year term, was widely seen as a referendum on Fox's presidency.
"We must redouble our efforts to successfully confront the demands of our citizens," Fox said Monday, indicating that he had understood the message from Sunday's defeat.
Personally, Fox remains popular, with a 65 percent popularity rating according to polls.
However, the president was unable to translate his charisma into more votes for his conservative PAN, which has enacted and supported policies seen as uncaring to Mexico's poorest.
One of the PAN's most stinging defeats was in the northern industrial state of Nuevo Leon, a former party stronghold, where the PRI candidate won the governor's office by a hefty majority.
Late Monday PRI candidates seemed certain to also take the governor's mansion in Sonora -- another northern former PAN stronghold -- as well as Campeche and Colima.
The PAN however retained control of Fox's home state of Queretaro, and was ahead in the central state of San Luis Potosi.
All 500 seats in the Chamber of Deputies were at stake in the Sunday vote, as were governorships in six of the country's 31 states and hundreds of town and city council seats.
Mexico's 128 senators do not face elections until 2006.
PRI leader Roberto Madrazo on Monday called for parties to work together to counter criminality, corruption and poverty, which affects about half the country, as well as rebuild economic growth.
In Washington, a US State Department spokesman praised the peaceful vote.
"Mexicans again demonstrated the strength of their democracy and the vitality of Mexico's democratic institutions," spokesman Richard Boucher said.
"After 70 years of one-party rule, we think that remains an enormously important outcome," he said.