South Korea's new president has a Trump-shaped crisis to avert

South Korea's new president, Lee Jae-myung, has secured a storming victory, but his honeymoon will barely last the day.

The former opposition leader is not getting to enjoy the two-month transition period usually afforded to new leaders, so they can build their team and nail down their vision for the country.

Instead he is entering office immediately, to fill the hole left by the impeachment of the former president, Yoon Suk Yeol, who last December tried and failed to bring the country under martial law.

In electing Lee, with almost 50% of the vote , South Koreans have vehemently rejected the military dictatorship that was almost forced upon them. Lee campaigned on the promise that he would strengthen South Korea's democracy and unite the country, after a divisive and tumultuous six months.

But that will have to wait. First, he has a Donald Trump shaped crisis to avert.

In the coming months, Trump has the power to destabilise South Korea's economy, its security, and its volatile relationship with North Korea.

South Koreans were dismayed when Trump slapped 25% tariffs on all Korean imports in April, after already hitting the country with aggressive tariffs on its core industries – steel and cars. They had assumed that being longstanding military allies from the days of the Korean War, and having a free-trade agreement with the US, would spare them.

If these tariffs take effect "they could trigger an economic crisis", a seasoned advisor to Lee's Democratic Party, Moon Chung-in, said.

Before Trump's announcements, South Korea's economy was already slowing down. The martial law chaos constricted it further. Then, in the first quarter of this year, it contracted. Fixing this has been voters' number one demand, even above fixing their beleaguered democracy.