Official campaigning for the Osaka mayoral election began Sunday, with Osaka Prefecture’s former governor, Ichiro Matsui, facing off against a ruling Liberal Democratic Party-backed challenger opposed to the controversial idea of restructuring the city into a metropolis.

The city of Osaka this month joined a number of local governments scheduled to hold gubernatorial, mayoral and assembly elections on April 7 after Osaka Gov. Matsui and Osaka Mayor Hirofumi Yoshimura both resigned in a bid to swap their positions. Matsui’s successor will also be picked on April 7.

Matsui, 55, and Yoshimura, 43, want to use the elections to push their political party’s goal of reshaping the city into a metropolitan government similar to that of Tokyo, which is intended to streamline the prefectural and city administrations.

The idea to form the “Osaka metropolis” — originally a pet proposal of former Osaka Mayor Toru Hashimoto — was put to a city referendum in May 2015, only to be rejected by voters. Matsui and Yoshimura were elected as governor and mayor respectively in November the same year, vowing to try again.

“We should not go back to a time when the overlapping operations of the prefecture and city were criticized,” Matsui said in a stump speech as the campaigning kicked off. “We will make Osaka a city that grows and where people are protected by the social security system.”

Akira Yanagimoto, a 45-year-old former assembly member of the city of Osaka who also filed his candidacy, called for the need to maintain the current city structure, saying, “It’s a great chance to bring an end to the Osaka metropolis concept.”

The gubernatorial race will be fought between Yoshimura and Tadakazu Konishi, a 64-year-old former Osaka deputy governor supported by the LDP.

Campaigning for mayoral polls in five other major cities across Japan, including Hiroshima, also began Sunday.