Politically, after Trump picked up the phone to talk to Taiwan’s President Tsai Ing-wen – and further agitated Beijing by refusing to commit to the one-China principle – it’s only natural that Beijing has to prepare for the possibility of a worst-case scenario for Hong Kong.

That may well explain why Beijing has repeatedly stressed recently that any collusion between independence advocates in Hong Kong and Taiwan will end in complete failure. It sends out a strong signal that national sovereignty and security will not be compromised, regardless of any policy change towards China that Trump may have in mind.

Still, Beijing’s worries will not go away easily. During the Occupy movement two years ago, Barack Obama promised President Xi that the US would not “interfere” in Hong Kong affairs, an undertaking that China would now regard as something already “gone with the wind”.

The US Congress aims to introduce a human rights act concerning Hong Kong “in the coming days” after Trump takes office, according to Marco Rubio, co-chair of the bipartisan Congressional-Executive Commission on China.

On the other hand, Stephen Yates, believed to be the man behind the Trump-Tsai phone call, is also an expert on Hong Kong. Beijing is understood to be watching closely whether or how Hong Kong may turn into a “bargaining chip” for Trump in Sino-US relations.

Economically, with Trump declaring a possible trade war against China, Hong Kong, as an open economy and the largest offshore centre for yuan business, can be in a very fragile position and even end up as a collateral victim. Also, as Leung pointed out, the impact of Brexit on Hong Kong cannot be ignored, although he stressed his administration was well prepared.

To add to the complexity of Hong Kong as an internationalised city, there is one point in Leung’s policy address that has not been widely reported, as significant as it is: as terrorist activities have become rampant in recent years, Hong Kong needs to enhance its emergency handling capability, including further reducing the risks of money laundering and terrorist financing through necessary legislation.

Yet the city does not lack long-existing thorny issues of its own, such as a shortage of land, soaring property prices and the widening wealth gap. All in all, it’s at such a time of many challenges and uncertainties that the city’s leadership race is heating up.

Beijing’s consideration of the right person to endorse will surely take into account all of these issues at home and abroad.

Of course, no one is perfect, but the four current chief executive aspirants – Lam, Tsang, former security chief turned lawmaker Regina Ip Lau Suk-yee, and retired judge Woo Kwok-hing – will be expected to rightly diagnose the problems and risks Hong Kong has to tackle internally and externally. And come up with solid and convincing policies to show their qualifications.