ROSARIO, Argentina, April 13, 2025 (AFP) - Argentine leader Javier Milei's small political party on Sunday faces its first electoral test since his presidency began, with a regional vote that could provide clues for October's midterm polls.

The election in Argentina's third-most-populous province of Santa Fe, with 2.8 million voters, will pick delegates to a convention set to reform the regional constitution, which has gone unchanged for 63 years.

Libertarian party La Libertad Avanza (Liberty Advancing, LLA) was created in 2021 to power the presidential ambitions of Milei, a telegenic economist-turned-member of parliament that same year.

At stake is whether the party can compete in regional politics, having surfed on Milei's personal brand to score a decisive 2023 presidential win with 55.6 percent of the vote.

Milei's ultra-laissez-faire economic policy has succeeded in slashing inflation, from 211 percent year-on-year in 2023 to 59 percent more recently.

He was rewarded Friday with the promise of $42 billion in support, a vote of confidence from several global institutions including the International Monetary Fund.

Milei's top political objective is the national legislative vote on October 26, when half of parliamentary seats and one-third of the Senate will be contested.

Vastly outnumbered in both chambers, LLA is under pressure to secure a firmer base in the legislature.

The administration has so far managed to pass laws only in rickety bill-by-bill alliances, leading to some stinging failures.

Recently, the Senate rejected two of Milei's nominees for the Supreme Court.

Although not a national vote directly on Milei's policies, Sunday's Sante Fe poll is "the first election since Milei became president and can give us an idea of the power of his brand," said political scientist Roque Cantoia of pollsters Doxa Data.

Milei scored 62.8 percent in Santa Fe in the presidential election, a remarkable performance for a candidate with little in the way of local party structures.

Just 25 percent of Santa Fe voters, however, identify with the president's party, Cantoia's research has found.

Recent national polls give Milei an approval rating of up to 45 percent.

He has sent his sister Karina, general secretary of his presidency, to kick off the local LLA chapter in Santa Fe.

She has toured multiple regions over the past year ahead of elections to provincial assemblies that will be a clearer test for Milei, with five set to be held in May alone.