He has held the post longer than anyone, including a grandfather and great uncle who were also prime ministers.

Our foreign affairs correspondent, Nick Schifrin, reports.

Shinzo Abe and his family are political veterans, but one of his lasting legacies may be an alliance with a political novice.

I grabbed him and hugged him, because that's the way we feel.

Donald, president, you are excellent businessman.

You have fought the uphill struggle and this is the dynamism of democracy.

He flattered President Trump. And he understood President Trump's personality.

Mike Mochizuki is the U.S.-Japan chair at George Washington University.

He says the Abe-Trump bromance, forged over sumo wrestling, golf selfies, and awkward handshakes, strengthened the bilateral relationship to confront China and North Korea and outlast Trump.

Minister Abe understood the strategic situation.

Without a strong U.S.-Japan relationship, Japan would not then have the autonomy and freedom to pursue its own interests in Asia.

Top of the list, a revitalized military.

Abe's Japan purchased more U.S. weaponry. He failed to revise the country's pacifist constitution, but pushed through changes that allow Japanese forces to fight in a crisis.

This opened the way for Japan to cooperate with other countries, especially the United States, on a variety of common defense missions.

Abenomics.

Economically, Abenomics lowered interest rates, increased spending, and pulled the economy out of deflation, but it achieved only modest success.

He did manage to end political instability and a rotating door of leaders.

Just to be able to stay in office this long, and to stabilize foreign policy, and chip away at some of the economic challenges, you know, that, in itself, I think, is a lasting achievement.

Abe leaves his successor with major structural economic concerns exacerbated by COVID (19).

And, today, in a final press conference, an emotional Abe said it broke his heart to leave the job half done.

For the "PBS NewsHour," I'm Nick Schifrin.