Shinzo Abe worked relentlessly at building close ties with American leaders, at Trump Tower and on the golf course with President Trump, and before then in Hiroshima and Pearl Harbor with President Obama.
The loss of Mr. Abe, who is stepping down because of poor health after driving U.S.-Japan relations for nearly eight years, will be one of the biggest risks as the allies tackle China’s military expansion and negotiate a renewal of the agreement under which Tokyo shares the costs for basing U.S. troops in Japan.
In a phone call on Monday Tokyo time—their 37th since Mr. Trump became president—the two leaders thanked each other for their trust and friendship, according to the Japanese side. On Twitter, Mr. Trump said the U.S.-Japan relationship had never been better and called Mr. Abe the greatest Japanese prime minister.
A close aide to Mr. Abe, Yoshihide Suga, emerged Tuesday as the front-runner in the race to succeed him after winning support from major factions in the ruling Liberal Democratic Party. But while Mr. Suga is well known in Japan as a behind-the-scenes enforcer of Mr. Abe’s policies, he has little diplomatic experience.
In a rare trip to the U.S. last May, Mr. Suga met Vice President Mike Pence and Secretary of State Mike Pompeo to discuss North Korea’s abduction of Japanese citizens in the 1970s and ’80s. If he becomes prime minister after a vote in Parliament in mid-September, Mr. Suga will likely immediately get to work developing a relationship with Mr. Trump.