Various surveys indicate Donald Trump will win the next U.S. presidential election. Polls conducted by major U.S. media outlets such as The New York Times and NBC News predict Trump's victory over his likely archrival President Joe Biden. Trump is now enjoying more than majority support from Republicans as the most promising presidential candidate for the November election.

Recently Trump drew attention by flamboyantly eulogizing his past "bromance" with North Korean leader Kim Jong-un. "After tough talk, then we fell in love," he said in a campaign rally at Cedar Rapids, Iowa, Dec. 2. This shows Trump's expected win will possibly provide fresh momentum for a breakthrough in the stalled North Korea-U.S. relations.

Notwithstanding such an optimistic perspective, however, many skeptics are wary of the potential adverse impact his win could have on South Korea-U.S. alliance and bilateral trade relations. They fear Trump may prefer policies that will undermine the South's interests mainly in security and economic terms.

For starters, during his stay in office, Trump labeled South Korea as a "free security rider." To Seoul's dismay, he asserted that South Korea had managed to protect itself by riding on the safeguard from the U.S. forces stationed here without paying due costs. Given this, he urged the South to sharply increase the defense cost share, even by five-fold.

With capricious foreign affairs and security policies, Trump endangered global alliances during his first term as president. In particular, he virtually shattered U.S. ties with the members of the North Atlantic Treaty Organization (NATO). While calling on NATO members to increase defense budgets, he revealed a negative viewpoint over the raison d'être of NATO itself. He was also amicable toward Russian President Vladimir Putin.

South Korea was never free from Trump's fickle behavior. In 2017 he threatened war with North Korea, aggravating military tension on the Korean Peninsula. Yet the following year, he again snatched global attention by showcasing his friendship with Kim.

His actions never ended as simple rhetoric. In 2018, he unilaterally suspended joint South Korea-U.S. military exercises without consulting the Moon Jae-in government, fresh from a summit with Kim in Singapore. Such honey between Kim and Trump seemed to have ended in the 2019 summit in Hanoi. Trump walked out of the meeting due to a difference in stances regarding the envisaged lifting of sanctions on the North in return for the demolition of the Yongbyon nuclear facilities.

According to memoirs of Trump staff, he stubbornly pushed to withdraw the U.S. troops from the peninsula but to no avail due to fierce opposition from the White House, State Department and Pentagon.

In this vein, his return to the White House is not welcome news for South Korea. Given the lingering nuclear threat from the North, concerns are brewing over the next Trump administration's Korean Peninsula policy. The Yoon Suk Yeol government has been desperate to expand U.S. nuclear deterrence. The Washington Declaration announced in April also focused on extended deterrence capabilities.

There has been growing anxiety that such an agreement will evaporate should Trump take power again. This is the reason why former National Security Office chief Kim Sung-han cited the need to utilize the "golden time" for implementing the nuclear deterrence plan before the presidential election next November.

North Korea has continued to build up its nuclear capabilities, including the much-touted intercontinental ballistic missiles (ICBMs) that can strike the U.S. mainland. Against this backdrop, it is almost impossible to deter the North's nuclear attacks with only the U.S.-provided nuclear umbrella unless South Korea is equipped with its own nuclear deterrence ability. And such risks could double should Trump retake power.

Besides security, concerns are also growing over Trump's attempted imposition of up to 10 percent duties on all imports. If he pursues such a policy again, it will deal a critical blow to the Korean economy, which is highly dependent on the U.S. market. Trump's possible protectionist policies will nudge other countries to follow suit, darkening the global trade environment.

Now it is high time for the Yoon administration to brace for the possibility of a new Trump administration, fortifying relations with officials who will be in charge of major policies. It needs to map out a contingency plan to prepare for the worst-case scenario of a possible withdrawal of U.S. forces.

The author is chief editorial writer at The Korea Times.