The Tokyo Metropolitan Assembly election on Sunday — in which Prime Minister Shinzo Abe's Liberal Democratic Party sustained a crushing defeat while Gov. Yuriko Koike's new party became the largest force in the assembly — marked Tokyoites' clearest thumbs-down of the Abe administration to date as much as it was their vote of confidence in the popular governor. Abe should take his first loss in major elections since his 2012 return to the government's helm seriously and reflect on what's the problem with his running of the administration on the strength of the ruling coalition's dominant grip on a Diet majority — which the outcome of Sunday's race suggests can be just fleeting.

The assembly race was the first electoral test of Koike since her own stunning victory in the gubernatorial election last August. The governor, who maintained a robust popular support rate of more than 60 percent in media polls, led her new Tomin First no Kai (Tokyoites First) party into the campaign. The party grabbed 49 of the assembly's 127 seats, and along with Komeito, which broke ranks with the LDP, its partner in the ruling alliance in national politics, in the metropolitan assembly and others, assembly members who support Koike now control 79 seats — well above the majority.

In a stark contrast, the LDP, which was earlier seen as competing neck and neck with Tomin First for the No. 1 position in the assembly, saw its pre-election strength of 57 seats dwindle to just 23 — far below its previous all-time low of 38 seats won in the 2009 race, held just before the party lost control of the government to the Democratic Party of Japan in the Lower House election.