President Mauricio Macri's coalition solidified its lead as Argentina's biggest political force in primary votes on Sunday that also saw the return of fiery leftist former leader Cristina Kirchner.
The compulsory votes are a formality to officially name the candidates teed up by their parties to fight the October 22 legislative elections.
Macri's liberal economic reforms in the poverty-stricken country appeared to have survived the test, two years into his term, with the Cambiemos coalition leading in the country's five biggest provinces.
"This is the change Argentines want," Macri told supporters.
"Results don't come overnight for things done seriously," he added, speaking to those suffering from the impact of inflation and unemployment, with about a third of the population living in poverty.
Much of the focus for the vote was on Buenos Aires, a province home to about 40 percent of voters that stretches from the capital to the Pampas plains, and Kirchner's results.
Kirchner, 64, dominated Argentine politics for years alongside her late husband before leaving office in 2015.
She scored 34 percent support for her bid to get a senate seat, despite facing corruption charges which she says are politically motivated.
Her score barely lagged behind ruling party candidate Esteban Bullrich, who got 34.3 percent with nearly 90 percent of the ballots counted.
A seat in the Senate would spare Kirchner jail if convicted of corruption. Her supporters hope it could also pave the way for a fresh presidential bid in 2019.
Her campaign is a headache for conservative Macri, 58.
He says his budget cuts are strengthening the economy but Kirchner and other critics say they are hurting the poor.
Macri lacks a majority in the legislature, where he has had to cobble together support for his reforms.
The October mid-term elections will be a major electoral harbinger for the Macri government, which is seeking to boost its foothold in parliament, where it is in minority in both chambers.
But Sunday's primaries already signaled a lack of structured opposition at the national level.
In the capital city, Macri-backed candidate Elisa Carrio got 48 percent of the vote, and government ally Martin Loustau got 13 percent.
Through his Cambiemos candidates, "Macri is looking to gain strength to ensure he can govern," sociologist Ricardo Rouvier told AFP.
"The opposition wants to send a message to the government that it is doing things badly."