Park Geun-hye is no longer president of South Korea. In the next 60 days, South Korea will hold special elections, an opportunity for the South to demonstrate the strength of its democratic institutions. The sharp contrast between the South's active participatory politics and North Korea's mafia-governance is on full display: The rule of law, not the rule of Kim Jong Un, reigns.

The impact of Park's impeachment is significant precisely because the South's formidable military, together with American forces, stands ever-vigilant against a despot completely bereft of morals. Both President Donald Trump and former President Barack Obama believe the North to be a grave threat to the U.S., and the next leader of South Korea will have considerable influence on the future of the U.S.-Korea alliance and how the world deals with North Korea in the short term.

The timing of scandals is never opportune. The indictment of Park's closest adviser on charges of extortion and abuse of power have occurred in parallel with an uptick in the North's bad behavior. In the past year and a half, the North has shown off its nuclear weapons capability, tested medium-range and intercontinental ballistic missiles and reportedly assassinated Kim Jong Un's half brother Kim Jong Nam with a banned VX nerve agent. Regardless of what you think about Kim Jong Un's leadership style, a nuclear warhead with the ability to reach California is not a capability you want in the hands of even the most level-headed actor. Kim may one day decide that it is in his best interest, and therefore rational, to strike U.S. military bases in Japan or troops stationed near the Demilitarized Zone into North Korea .

The North's recent provocations and stakes-raising are amplified by the impeachment. Park's conservatives, the party of reliable North Korea hard-liners, is now in tatters, perhaps unable to nominate a candidate for the special election. The election's outcome could lead to a wavering of U.S.-Korea resolve at precisely the moment when firm commitment is needed.

The challenge of dealing with North Korea and the results of the special election are thus intimately intertwined. Informed observers and recent polls suggest that Moon Jae-in, the liberal runner-up to Park in the 2012 election, will be the front-runner. Moon's politics purportedly closely mirror former President Roh Moo-hyun's; exactly how much is not yet known. During Roh's tenure, his government confounded the Bush administration on North Korea policy but simultaneously supported the U.S. in Iraq by deploying South Korean troops to Kurdistan.

Clearly, diplomacy will play a key role going forward. It is essential that the Trump administration foster closer ties and develop shared objectives. To do so, the administration should immediately fill important diplomatic posts such as ambassador to South Korea and Japan. And while many observers are pointing to the deployment of U.S. anti-ballistic missile forces, known as Terminal High-Altitude Area Defense system or THAAD, to South Korea as a potential wedge issue exploitable by China, the administration should not let policy myopia distract from the main North Korea challenge.

I participated in a recent track-two dialogue in China. Our interlocutors' objections to the THAAD deployment dominated the conversation. But these protests obscured an unavoidable fact: that the U.S., South Korea and China share the same goal of ensuring peaceful outcomes on the peninsula. The exact way forward needs to be closely coordinated without losing the main idea: A North Korea with a nuclear-armed missile capability represents an unacceptable risk for U.S. national security.

Ultimately, the political issues in South Korea will force the Trump administration to confront – head-on and early in the president's term – the key issue of sustaining U.S. security leadership around the world. America has greatly benefited from the post-World War II order, and nowhere has our stabilizing presence been more important than in East Asia.