The party of Mexican President Vicente Fox has been dealt a blow in regional elections in its northern heartland.
Fox was dealt a double blow as an aide resigned over the role of the first lady
It failed to recapture the northern states of Chihuahua, Durango, or Zacatecas. Zacatecas instead elected the country's only woman governor.
There was a corresponding resurgence of Mexico's previously dominant - and then discredited - PRI party.
President Fox suffered another setback on Monday, when his chief aide resigned over "policy disagreements".
Private secretary Alfonso Durazo said he was particularly displeased about the increasing political influence being exerted by President Fox's wife, Marta Sahagun.
Old party boost
These elections in three states are the first of 10 elections for regional executives this year.
The states of Chihuahua and Durango saw convincing double-digit wins for the Institutional Revolutionary Party (PRI).
The PRI also snatched the mayorship in the city of Ciudad Juarez in Chihuahua.
Analysts say the results are a huge boost to the PRI - which was thrown out of power in 2000, ending 70 years of one-party rule.
They augur badly for President Fox's National Action Party (PAN), which faces regional elections in seven more states later this year - and a presidential poll in 2006.
The crowning glory for the PRI was its 14-percentage-point lead in Chihuahua - home of PAN founder Manuel Gomez Morin and an early outpost of opposition to the PRI in the 1990s.
"The PAN is on its way out in the northern part of the
country," Roberto Madrazo, head of the PRI and the party's likely presidential candidate, said in a statement.
"Their time of dominance is over."
But Cesar Juaregui, a PAN senator from Chihuahua,
downplayed the PRI victories.
"How much will this matter for 2006? Very little," he told reporters.
"Things are just getting started. They change from one day to the next."
But he added that "the PAN must recognise it has made errors".
Women wins governorship
Meanwhile, there was a historic win for Amalia Garcia of the Democratic Revolution Party (PRD) in Zacatecas state.
She becomes Mexico's first elected woman governor since 1989, after winning 47% of the vote against 34% for PRI candidate Jose Bonilla.
She is only the third woman governor since women gained the vote in Mexico in 1953.
Garcia said women voters had flexed their muscles
Ms Garcia, who is the daughter of a governor, attributed her win to the large proportion of female voters in a state in which many men have migrated to work in the United States.
"Never before had I seen women so involved in the
political process and in leadership roles in their
communities and this is a result of migration," she reportedly said in an interview with TV network Televisa.
In another blow to President Fox, his top aide Alfonso Durazo resigned on Monday, citing in particular the presidential ambitions of first lady Marta Sahagun.
"The country has certainly advanced politically, enough
that it is ready for a woman to reach the presidency of the republic," Mr Durazo said in his 19-page letter.
"Nonetheless, it is not prepared to have the president leave the presidency to his wife."
In an especially cutting comment, Mr Durazo compared Mr Fox's rule to the reign of the PRI. Mr Fox came to power on the slogan of the "government of change".
"The desire for a government to decide who the next
president will be or won't be was the original sin of the
old regime," Mr Durazo wrote.
Ms Sahagun has not formally declared any presidential ambition, but is an active party campaigner and runs her own charitable foundation.
Her activism has angered some within Mr Fox's own party, who complain she has an unfair advantage.
But a political analyst told the BBC that Mr Fox's acceptance of Mr Durazo's resignation demonstrates his reluctance to curb his wife's growing authority.