FILE PHOTO: Argentina's President Mauricio Macri speaks during a meeting with Brazil's President Jair Bolsonaro in Brasilia, Brazil, January 16, 2019. REUTERS/Ueslei Marcelino/File Photo

BUENOS AIRES (Reuters) - Argentina´s opposition posted big wins in provincial elections on Sunday, months ahead of a presidential showdown pitting incumbent Mauricio Macri against a Peronist ticket that includes former President Cristina Fernandez in the No. 2 spot.

The elections took place as a countrywide blackout left tens of millions without power in the South American nation. Voting was delayed but went ahead despite the outage.

Argentina faces an economic crisis that has plunged nearly a third of the country into poverty, pushed interest rates skyward and sent the peso tumbling against the dollar, prompting mass protests.

Peronists and centre-left allies held strong leads in elections for governor in the provinces of Tierra del Fuego, Formosa and San Luis, early results showed. Polls showed a close race between a Peronist and a Socialist candidate in the province of Santa Fe.

The strong showing by the opposition in the provincial elections was broadly seen as a good sign for the Peronist presidential ticket led by Alberto Fernandez, although recent opinion polls showed the Peronists with only a slight lead over the centre-right Macri ahead of the Oct. 27 vote.