Julio Cobos broke from the opposition Radical Civic Union party to campaign with Fernandez, the wife of President Nestor Kirchner, who took office in 2003 and oversaw Argentina's recovery from economic collapse.

Cobos told a crowd of about 5,000 that he and Fernandez were united by convictions if not party affiliation.

"We are people from different political groups that want a different Argentina," Cobos said.

Cobos, 52, has governed Mendoza since 2003. The mountainous province is famed for its fine wine and ski slopes. He is married, with three children.

Approval ratings for Kirchner's center-left administration have been buoyed by years of robust economic growth following Argentina's 2002 financial meltdown. But his popularity has dipped in recent months amid high inflation, an energy crisis and corruption scandals.

With incumbents barred from seeking more than one consecutive re-election, some have speculated that Kirchner and his wife plan to alternate in power.

Fernandez is drawing comparisons to Eva "Evita" Peron, the charismatic former first lady and second wife of late strongman Juan Domingo Peron.