The impeachment of pro-Western President Park Geun-hye has raised the possibility that the countrys next leader will be from one of the left-of-centre opposition parties leading the charge against her.
Those parties are deeply critical of the close strategic relationship South Korea has with Washington and its allies, including Australia. They support a softer, less forceful line than Ms Park has taken towards North Korea. The left-wing South Korean parties are also less critical of Chinese support for the rogue state.
Beijing would welcome a more malleable, less pro-Western regime in Seoul as it expands in the South China Sea.
Barack Obama and Mr Trump must leave Pyongyang and China in no doubt that any adventurism aimed at taking advantage of current instability in South Korea will not be tolerated. Mr Trump was ambivalent during the campaign about US support for South Korea. But after his victory he assured Ms Park he would preserve the security alliance. He must not waver.
