Official campaigning commenced Thursday for a House of Councillors by-election in western Japan, the first national contest since Prime Minister Fumio Kishida revamped his Cabinet last month in a bid to re-energize his political base.

The upper house race in the Tokushima-Kochi district kicked off before campaigning for a House of Representatives by-election starts next Tuesday. The two by-elections on Oct. 22 are expected to be one-on-one battles between the ruling and opposition forces.

The by-elections come as the approval ratings of Kishida's Cabinet have slumped to the lowest levels since he became prime minister in October 2021, due in part to public frustration over surging prices and insufficient wage growth.

One of the major focuses of the by-elections is whether voters will support a new economic package that Kishida has pledged to finalize by the end of the month, including steps to mitigate the adverse effects of cost-push inflation.

People gather to listen to stump speeches in Tokushima on Oct. 5, 2023, as official campaigning commenced the same day for a House of Councillors by-election in the Tokushima-Kochi constituency. (For editorial use only)(Political party posters and other parts of photo pixelated)(Kyodo)

"We will definitely realize growth in regional areas through measures to address rising prices and wage hikes," Toshimitsu Motegi, secretary general of the Liberal Democratic Party headed by Kishida, said in the city of Kochi.

In Tokyo, Kenta Izumi, chief of the main opposition Constitutional Democratic Party of Japan, said the by-election would provide an opportunity to grill the Kishida government, which "has not been able to revitalize regional economies."

The results of the by-elections are likely to affect whether Kishida dissolves the lower house for a snap election during the extraordinary parliamentary session slated to be convened on Oct. 20, political experts said.

The LDP is fielding Ken Nishiuchi, a former Kochi prefectural assembly member, in the upper house by-election, with the backing of its junior coalition partner Komeito party.

Hajime Hirota, a former lower house lawmaker of the Constitutional Democratic Party of Japan, is running as an independent candidate with the support of several opposition groups.

The upper house seat, which covers both Tokushima and Kochi prefectures, became vacant after then LDP lawmaker Kojiro Takano stepped down in June after it was revealed he assaulted his secretary.

Such merged districts combining sparsely inhabited neighboring prefectures were introduced in 2016 to reduce the disparity in the weight of votes between more and less populated areas.