Argentine President Maurico Macri's centre-right coalition was ahead in mid-term elections on Sunday, putting him on course to strengthen his hand to carry through pro-market economic reforms, partial results showed.
Mr Macri's Cambiemos coalition was in the lead in 15 of Argentina's 23 provinces as well as in the capital Buenos Aires, according to partial results released by the central electoral authority at 10pm local time.
Ex-president Cristina Kirchner was virtually certain to take a seat in the senate with 70 per cent of the vote counted, despite trailing Macri candidate Esteban Bullrich in the key province of Buenos Aires, an area the size of Italy.
A senate seat would mark a return to the political fray for the 64-year-old Ms Kirchner, a key Macri critic, and guarantee her parliamentary immunity from a string of corruption charges.
Sunday's election was largely a referendum on Mr Marci's two years in office, in which he was seeking a mandate to further overhaul an ailing G20 economy.
He has so far managed to push through a painful reform program with the help of allies in parliament, despite having only 87 seats in the 257-seat Congress and 15 of 72 senate seats.
Seat projections were not expected before early Monday.