LONDON/NEW YORK ¨C Steve Schwarzman, chief executive officer of Blackstone Group LP, who recently returned from South Korea, offers a polite answer to the question everyone keeps asking: ¡°It¡¯s very colorful.¡±

Henry Kravis, co-founder of KKR & Co. LP, is more blunt: ¡°Nobody can figure it out.¡±

And Don Marron, chairman of Lightyear Capital LLC, captures what amounts to a collective shrug: ¡°What do you say? ¡®It¡¯s a mystery¡¯ is what you say.¡±

The question, the one being thrown at American executives in London, Hong Kong and Berlin ¡ª and pretty much wherever else they go ¡ª is this: How did Donald Trump become a serious contender for the U.S. presidency?

The answers, in public at least, are a mix of genuine befuddlement and careful messaging as Trump has gone from long shot to presumptive Republican nominee and is now closing the gap in national polls with Hillary Clinton, his Democratic counterpart.

By courting support largely from low-income voters who feel left behind by economic forces, Trump has shaken up the 2016 race, caught executives by surprise and dominated the conversation in international business circles like no other U.S. presidential contest in recent memory.

Apart from Amazon.com Inc. CEO Jeff Bezos, who in December tweeted ¡°#sendDonaldtospace¡± after Trump accused him of buying the Washington Post to keep his taxes down, few executives want to get in the middle of this wildly contentious election season. Why risk offending customers, let alone Trump and his almost 9 million Twitter followers or Clinton and her supporters? They also don¡¯t want to let politics dominate business discussions.

Good luck with that. Privately, some executives say many colleagues and customers overseas are transfixed by this election season, and particularly by the Trump phenomenon. One U.S. banking official said he was bombarded non-stop with questions during a recent business trip to Hong Kong and Tokyo.

They asked, ¡®Can he become president? Is this literally possible?¡¯ said the executive, who, like many, spoke on condition he not be named. That¡¯s all they wanted to talk about, he added.

Investors are only beginning to assess the impact of a Trump or Clinton win in November.

At Pacific Investment Management Co.¡¯s secular forum last month ¡ª when the firm brought in Ben Bernanke, Jean-Claude Trichet and Gordon Brown to talk about the long-term economic and market outlook ¡ª they discussed Trump as a sign of rising anti-establishment sentiment in the U.S. and Europe, said Pimco Group Chief Investment Officer Daniel Ivascyn.

¡°We¡¯re spending some time on the implications of what a Trump presidency or a Clinton presidency might mean for the markets,¡± Ivascyn said. ¡°We¡¯re cautious long-term. It¡¯s not specific to Trump.¡±

As a global media frenzy rages over...