Official campaigning began Thursday for Japan's House of Councillors election, with Prime Minister Shinzo Abe seeking to maintain political stability to press ahead with the first-ever constitutional revision and a planned consumption tax hike.

The July 21 poll comes amid heated debates between ruling and opposition parties over a controversial estimate on required levels of retirement savings that sparked concerns about the pension system's ability to provide for people in rapidly aging Japan.

(Japanese Prime Minister Shinzo Abe, head of the Liberal Democratic Party, makes a speech in Fukushima on July 4, 2019.) 

The October tax hike -- from 8 percent to 10 percent -- that is likely to hit household spending, is also a hotly-contested topic.

The focus of the nationwide upper house election, the first since 2016, is on whether a two-thirds majority can be reached to initiate a referendum on a change in the Constitution. The ruling coalition will need to retain the support it has from other like-minded lawmakers if it is to attain Abe's controversial but long-held goal.

"It's an election to choose from parties that have responsible lawmakers who discuss the issue (of constitutional reform) or parties that do not want to hold deliberations," Abe said in a speech in Fukushima Prefecture, northeastern Japan.

A total of 370 people have registered their candidacies to vie for the 124 seats up for grabs, 74 to be chosen in electoral districts and 50 through proportional representation.

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Major political parties' election pledges on key issues

(Leaders of the major Japanese political parties -- (from L) Ichiro Matsui of the Japan Innovation Party, Natsuo Yamaguchi of the Komeito party, Yukio Edano of the Constitutional Democratic Party of Japan, Prime Minister Shinzo Abe of the Liberal Democratic Party, Yuichiro Tamaki of the Democratic Party for the People and Kazuo Shii of the Japanese Communist Party)

Under changes to the system, some will be elected through proportional representation according to their place on each party's priority list, regardless of the number of votes they get as individuals.

The ruling Liberal Democratic Party, headed by Abe, hopes to secure a majority in the 245-member upper chamber with coalition partner Komeito.

With 70 seats not being contested, it means that the coalition needs to win at least 53, fewer than the 69 seats it won in the previous upper house election in 2016. To gain the desired two-thirds majority, the LDP-Komeito coalition, along with other pro-revision opposition and independent lawmakers, need to win a combined 86 seats.

The election will be held as the six-year term for half of the current upper house members will expire on July 28.

Due to electoral system reform in July 2018, the number of seats in the upper house will rise by six from 242 to 248 in two stages, with three of the six to be added this time to bring the total seats to 245.

Opposition parties are joining forces to counter the ruling bloc and to avoid splitting their vote by fielding "unified" candidates in the country's 32 single-seat constituencies.

(Passers-by stop and listen to a politician speak on the streets of Tokyo on July 2, 2019.)

The 17-day campaign period will give Japanese voters the time to look back over the six and a half years of the Abe government since it was elected in December 2012. Voters will assess the priority it has put on reviving the world's third-largest economy under its "Abenomics" policy program.

"People's livelihoods have been destroyed...since the launch of the Abe administration" in 2012, Yukio Edano, leader of the largest opposition Constitutional Democratic Party of Japan, said in a stump speech in Tokyo's Shinjuku Ward.

"Let us make it an election to protect and defend our livelihoods."

(Yukio Edano, head of the main opposition Constitutional Democratic Party of Japan, makes a speech in Tokyo on July 4, 2019.)

The ruling and opposition parties are split over amending the pacifist Constitution and raising the consumption tax.

The LDP aims to revise the Constitution "at an early date" while Komeito is more cautious about doing so. The Constitutional Democratic Party of Japan, the Democratic Party for the People, the Japanese Communist Party and the Social Democratic Party, are against changing the supreme law.

But when it comes to Abe's wish to clarify the status of the Self-Defense Forces in Article 9 of the Constitution, over half of the candidates expected to run, no matter which party they represent, are opposed, according to a recent poll by Kyodo News.

The economy is expected to be a critical issue for voters amid signs that a U.S.-China tariff war has been weighing on Japan's growth ahead of the planned consumption tax hike.

The LDP and Komeito stress the need to raise the tax to enhance social security services but all five major opposition parties, including the Japan Innovation Party, are opposed to hiking it and rather put their emphasis on supporting households.

The Abe government has already decided to use part of the expected revenue from the tax increase to enhance childcare support, preparing steps against any negative impact of the tax rise on the economy after the previous hike crimped consumer spending when the tax rate rose from 5 percent to 8 percent.

Opposition parties are stepping up criticism against the government over its refusal to receive a pension report from a panel of experts that estimates the average retired couple would face a shortfall of 20 million yen ($185,000) under the current pension system if they live to be 95 years old.

Finance Minister Taro Aso, who oversees the Financial Services Agency that formed the panel, has said that it contradicts the government's view that the pension system serves as the basis of household finances during post-retirement years. Abe has pledged to improve social security services for "all generations."