A House of Representatives by-election, the first national-level contest since the April 1 tax hike, will be held in Kagoshima Prefecture on Sunday to fill a seat formerly held by a ruling party lawmaker who resigned in February over illegal election campaigning.
Voters are expected to focus on the issue of "money and politics" and the how the tax hike to 8 percent from 5 percent is affecting their lives.
The by-election in Kyushu is expected to be a battle between the ruling Liberal Democratic Party's Masuo Kaneko, 67, a former chief of the prefectural assembly who is backed by junior coalition partner New Komeito, and Akashi Uchikoshi, 56, backed by the Democratic Party of Japan and three other opposition parties.
Kaneko has promised to stimulate the local economy with the help of Prime Minister Shinzo Abe's economic policies.
Uchikoshi has pledged to seek transparency and get to the bottom of the money scandal that cost former Lower House lawmaker Takeshi Tokuda his seat.
Tokuda resigned over the scandal, which involved illegal campaigning by his family members in the 2012 election.
The number of eligible voters in Kagoshima stood at 278,643 as of April 14.