Donald Trump’s victory in the US presidential election left European leaders struggling to formulate an appropriate response. French president François Hollande, who once claimed Trump’s excesses made you want to retch, spat out his strained congratulations, leaving no doubt that his greeting was for form’s sake alone.

A rather more dignified message from German chancellor Angela Merkel was short and pointed. She said her close cooperation with Trump would rest on their countries’ shared values of “democracy, freedom, respect for the rule of law and the dignity of men, regardless of origin, skin colour, religion, gender or sexual orientation”.

European Council president Donald Tusk and Jean-Claude Juncker, president of the European Commission, joined in the formal congratulations. They invited him to Brussels to discuss the transatlantic relationship.

Out of the public eye, the mood was sombre. Brexit Britain aside, of the 27 remaining member states, all but Hungary’s Viktor Orbán had expressed a clear preference for a Hillary Clinton presidency. They were so clear, in fact, that an unspoken taboo had stifled any real discussion of the alternative. On the morning of November 9, Europe woke up to that alternative – and to a flurry of informal diplomatic activity.

A special meeting for European foreign ministers was called to assess the potential impact of Trump’s “America first” approach. British foreign minister Boris Johnson dismissed this as a “collective whingerama” and refused to attend.

Merkel is also combining a state visit by incumbent US President Barack Obama with a meeting of the heads of state and government of France, UK, Spain and Italy, no doubt to discuss strategy and contingency planning.

Of greatest concern to European leaders is the fact that Trump is an unknown quantity, without prior government or military experience. The world knows what he said on the campaign trail, but not how he might actually perform in office.

This spooks many, including German foreign minister Frank-Walter Steinmeier, who believes that transatlantic relations are set to become both more difficult and more unpredictable. There is also concern about Trump’s open admiration for the authoritarian leadership style of Russian president Vladimir Putin.

Tension over NATO

Many European leaders fear that the US president-elect’s apparent indifference to western liberal democratic process and values, together with a deterioration in the transatlantic relationship, may tarnish the western alliance in the eyes of the world. In geostrategic terms, such a loss of credibility could play into the hands of an emerging Russian-Chinese alliance.

Guy Verhofstadt, the designated Brexit-negotiator for the European parliament, does not mince his words. He has noted that Trump’s stated priorities are not Europe’s priorities and that Europe should no longer depend on the US.

Within this context, European security is high on the EU’s post-election agenda. During his campaign, Trump made overt references to the contentious issue of “burden-sharing” within the NATO alliance. The US has long held that it pays too much for Europe’s defence through this partnership.

Europe sees NATO’s main role as largely to engage in “soft security” while the US would prefer EU countries to adapt to regional hard security challenges and to take greater responsibility – both strategic and financial – for defending the European continent. Trump has intensified this tension by referring to NATO as “obsolete”.

He has even suggested making US defence assistance to other countries contingent on payment, which is untenable under the NATO charter.

A threat to the European project

Trump’s aggressive protectionist outlook also casts doubt on the future of the controversial Transatlantic Trade and Investment Partnership between the US and the EU.

This may lead to a scramble for bilateral deals, led by Brexit Britain. Prime minister Theresa May is set on a more pragmatic course based on the UK’s “special relationship” with the US – but that’s a course branded by the German MP Axel Schäfer as “delusional”.

The fact that arch eurosceptic Nigel Farage was the first foreign politician to win an audience with the president-elect hints at acrimonious relations to come between the UK and the remaining member states over transatlantic relations.

Ominously, according to a Moody’s, Trump’s economic proposals would result in a two-year-long recession in the US and a sharp increase in unemployment. Combined with the eurozone crisis and the economic uncertainty over Brexit, a US downturn might push Europe back into recession too.

Trump’s openly populist appeal, on top of the rhetoric of the recent Brexit referendum campaign, has raised the spectre of a pendulum swing away from the high ideals and integrative ambition of the European project back to the authoritarianism and intolerance of darker times in European history. As Tusk stated: “The events of the last months and days should be treated as a warning sign for all who believe in liberal democracy.”

And indeed, Trump’s victory was greeted with glee by the leaders of Europe’s populist radical right-wing parties.

No wonder European leaders are mustering. The UK and US votes have the potential to mark a decisive moment in the mainstreaming of populism as a legitimate electoral ideology. That calls for a meaningful response.

Patricia Hogwood does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond the academic appointment above.

This article was originally published on The Conversation. Read the original article.