Osaka voters headed to the polls Sunday to vote for a second time on whether the city should become a metropolis akin to Tokyo in 2025.

Backed by Osaka Gov. Hirofumi Yoshimura and Mayor Ichiro Matsui, the initiative calls for the restructuring of Osaka city's 24 administrative districts into four special wards with greater authority and elected leaders. Tokyo is arranged similarly with 23 special wards.

Proponents say the measure will lead to cost-effective governance by eliminating duplication of work by the Osaka prefectural and city governments. Opponents, however, argue the coronavirus crisis should be prioritized over the referendum.

Some 2.2 million voters in the city are eligible to take part in the binding referendum, for which official campaigning started on Oct. 12.

A Kyodo News poll showed last Sunday that 43.6 percent of voters were opposed to the plan while 43.3 percent supported it, making for another tight race.

A similar plan was voted down in 2015 by a slim margin, but Matsui, who heads Nippon Ishin no Kai and the regional political group Osaka Ishin no Kai, said that since Toru Hashimoto, a former governor and mayor of Osaka, first advocated for the plan in 2010, the city's economy has grown too large to administer in the current way.

If the plan is voted down again, Matsui has said he will retire from politics after completing his term as mayor through April 2023.

The Osaka metropolis plan is the signature policy of Osaka Ishin no Kai. Komeito, the ruling coalition partner of the Liberal Democratic Party, also backs the plan.

But opponents, including the LDP and the Japanese Communist Party, argue that, if implemented, the plan will deliver a hit to the area's coffers, worsen services for residents and be an impediment to disaster prevention efforts.