The Tokyo No. 1 district, at the heart of the capital, has always been a competitive electoral battleground for candidates of the two largest parties — the ruling Liberal Democratic Party and the opposition Constitutional Democratic Party of Japan.

The district, which straddles Shinjuku and Chiyoda wards, has nine candidates vying for a single seat. But two candidates are the clear front-runners ahead of Sunday's Lower House election: Miki Yamada of the LDP, and veteran CDP lawmaker Banri Kaieda.

Yamada, who won the district seat in the last general election, is up against the wall for her involvement in a series of political slush fund scandals that has shaken the LDP since late last year.