TOKYO • Japan's main opposition Democratic Party (DP), whose three years in power from 2009 to 2012 have been characterised by mismanagement, is still suffering from single-digit approval ratings.

Yet it pulled off an electoral upset on Sunday that has sent ripples through the nation, when the DP- backed candidate was elected mayor of Sendai, the largest city in the Tohoku region, which was ravaged by the 2011 earthquake and tsunami.

Ms Kazuko Kori, 60, won 43 per cent of the total votes cast, edging out the candidate backed by the ruling Liberal Democratic Party (LDP), Mr Hironori Sugawara, 57, who won 38.7 per cent.

This is the LDP's second major electoral setback in three weeks, as Prime Minister Shinzo Abe's party suffers the fallout from a series of gaffes and scandals that has sunk his once-Teflon ratings to new lows.

On July 2, the LDP was hammered at the Tokyo assembly election, when more than half of its original 57 lawmakers were ousted by a young upstart party. And Mr Abe was heckled when he spoke at the Akihabara electronics district on the eve of the Tokyo election.

The two election defeats, along with a string of media opinion polls showing nose-diving public opinion towards Mr Abe and his Cabinet, suggest an uphill battle for the LDP in winning back public confidence.

A poll by the left-leaning Mainichi Shimbun at the weekend shows Mr Abe's approval rating plunging to 26 per cent, down 10 points from the last survey last month, while a poll by business daily Nikkei also saw a 10-point drop, to 39 per cent.

The LDP's election strategy committee chairman Keiji Furuya said in the wake of Sunday's defeat in Sendai that the result was "influenced by national affairs".

Walter Sim