Momentum for campaign cooperation among opposition parties in this summer's Upper House election isn't growing. Democratic Party of Japan leader Katsuya Okada stresses that the opposition camp must stop Prime Minister Shinzo Abe's ruling coalition and its allies from winning a two-thirds majority in the Upper House — the threshold for initiating an amendment to the Constitution that Abe's bloc already clears in the Lower House — but does not appear to have a clear prospect on how, after the opposition parties were crushed by the Liberal Democratic Party-Komeito alliance in the past three national elections in a row.

As it is, the splintered opposition camp again risks failing to put up a viable alternative to Abe's ruling coalition and leaving voters with little choice — a familiar picture that should not be repeated, if just for the sake of bringing back some healthy competition in national politics.

Last summer, popular approval ratings of Abe's Cabinet sharply plunged as his ruling coalition railroaded the contentious security legislation through the Diet, but that did not lead to an increase in public support for the opposition camp, which has effectively been powerless against the LDP-Komeito alliance's dominant grip on the Diet since the DPJ fell from power in 2012. Public support for the Abe Cabinet has since recovered, leaving the opposition parties trailing far behind his LDP.