Prime Minister Shinzo Abe's abrupt decision to resign has caught Japan off guard at a moment of great uncertainty as the global coronavirus pandemic poses unprecedented challenges for the country.

The announcement on Friday of his impending resignation, which Abe attributed to his state of health, came as a surprise but also a deja vu for many people who saw him step down in 2007 due to the worsening of his illness -- ulcerative colitis -- during his first stint as the nation's leader.

Women read an extra edition of a newspaper in Tokyo on Aug. 28, 2020, after media reported that Japanese Prime Minister Shinzo Abe will step down from his post due to a health problem. (Kyodo)

The 65-year-old called it quits only a few days after he became the longest-serving prime minister in terms of consecutive days in office and his recent hospital visits sparked concerns that his health may be deteriorating.

"It will change the political situation in Japan," said Jun Azumi, the Diet affairs chief of the main opposition Constitutional Democratic Party of Japan. "It is the most significant event in a decade."

Since Abe's return to power in 2012, Japan has experienced years of political stability underpinned by a series of election wins that political experts have attributed to a fractured opposition rather than to particular policies of Abe and his Liberal Democratic Party.

His stable power base has also made him a familiar face among world leaders including U.S. President Donald Trump, with whom Abe has built close ties.

But in recent months, Abe has faced an uphill battle after coming under fire for his handling of the coronavirus outbreak.

"Politics is not about how many days one has stayed in office, but what one has accomplished," Abe told reporters on Monday as he marked 2,799 uninterrupted days as premier, the longest stretch on record.

Abe's current term as LDP president -- and thus prime minister -- was to expire in September 2021 and he had indicated that he would not seek another term.

Critics say Abe has achieved little despite serving for a record length in office. "He tried to build a legacy (that would characterize his tenure) but the only legacy will be the length of time in office," said Hitoshi Komiya, a professor of modern Japanese political history at Aoyama Gakuin University in Tokyo.

Speaking at a press conference to announce his resignation on Friday, Abe did not say who he thinks should succeed him, only saying it is up to the LDP to decide. The ruling party will hold a leadership election in September to pick his successor.

Several LDP lawmakers have been floated as potential candidates. They include former Foreign Minister Fumio Kishida, who is now the party's policy chief, former Defense Minister Shigeru Ishiba, a critic of Abe, and Chief Cabinet Secretary Yoshihide Suga.

As Komiya suggested, Abe leaves office with a list of unattained goals -- amending the Constitution for the first time since its promulgation after World War II and making the Tokyo Olympics and Paralympics a success in the summer of 2021 after a one-year postponement due to the coronavirus.

A large screen in Osaka's Dotonbori commercial district shows the news on Aug. 28, 2020 that Japanese Prime Minister Shinzo Abe announced his intention to resign, citing a health problem. (Kyodo)

No major breakthrough was made in resolving the issue of North Korea's abductions of Japanese nationals in the 1970s and 1980s, which Abe said was "gut-wrenching" because he placed priority on it.

The economy is at a critical point as it posted an annualized real 27.8 percent contraction in the April-June quarter, the steepest fall on record due to the pandemic, casting doubts over years of his "Abenomics" policy mix featuring massive monetary easing by the Bank of Japan.

After becoming Japan's youngest prime minister in 2006, Abe suddenly resigned the following year, citing ill health, ushering in an unstable period of "revolving-door" politics as the country saw several prime ministers come and go.

Public dissatisfaction with the LDP had grown as the two prime ministers that followed Abe -- Yasuo Fukuda and Taro Aso -- both stepped down after serving for only about a year each while the economy was reeling in the midst of the global financial crisis following the collapse of Lehman Brothers Holdings Inc. in 2008.

About five decades of uninterrupted rule by the LDP ended in 2009 after the then-Democratic Party of Japan scored a historic victory in a general election.

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