Osaka Mayor and Nippon Ishin no Kai (Japan Restoration Party) founder Toru Hashimoto will be appointed coleader of the party in a move designed to heal the rift between the Osaka faction and Shintaro Ishihara that is threatening the party’s prospects in this summer’s Upper House election.

Osaka Gov. and Nippon Ishin Secretary General Ichiro Matsui made the announcement Wednesday in Osaka, saying party leaders will formally endorse Ishihara and Hashimoto as coleaders Saturday.

“By moving Hashimoto (to coleader), Ishihara’s burden can be reduced. There are lots of television programs a party leader needs to appear on in the run-up to the Upper House election, and we were worried about Ishihara’s physical condition,” Matsui said.

Ishihara is 80 years old.

Many around Hashimoto and Matsui have grown concerned that differences in policy, personality and political style between Ishihara and his allies in Tokyo and the Osaka faction will lead to a voter backlash in the July Upper House election.

Since the Lower House election last month, in which Nippon Ishin won 54 seats, Ishihara has kept a low media profile, while Hashimoto and Matsui have become more prominent, recently announcing plans, from Osaka, to field more than 60 candidates in the Tokyo Metropolitan Assembly election this summer.

Last week, Prime Minister Shinzo Abe traveled to Osaka to meet with Hashimoto and Matsui, and earlier this week both attended a New Komeito gathering in Osaka, where Hashimoto called for including the Liberal Democratic Party in the ruling coalition with Nippon Ishin and New Komeito.

Hashimoto’s local group, Osaka Ishin no Kai, does not have a majority in the Osaka Municipal Assembly and needs New Komeito’s cooperation to pass legislation.

Ishihara has said little about such moves by Hashimoto, but many Osaka members have long doubted his commitment to a key platform plank, the integration of Osaka Prefecture and the city of Osaka. Ishihara had long opposed calling the merger “Osaka-to,” because the Japanese for “to” means “capital” and Tokyo is officially known as “Tokyo-to.”