More than halfway through this year of momentous elections, liberal democratic parties have mostly managed to hold the line against the advance of the dark forces of nationalist populism in Europe. Yet it is too early to declare victory for this firewall against the extreme right. The US presidential election could have destabilising knock-on effects in Europe and beyond if Donald Trump returns to the White House. On the other hand, a victory for the vice-president, Kamala Harris, who has restored the Democrats’ hopes of retaining power in just three weeks since President Biden pulled out of the race, could energise progressive forces around the world. In Europe, the loose alliance of mainstream parties that has kept the forces of illiberalism, intolerance and bigotry out of power in Brussels, Paris, Berlin and Warsaw is fragile. They have been aided by the congenital inability of hard-right parties, which won about 25% of the vote in EU-wide elections in June, to form a united front in the European parliament. Despite the attempt of Hungary’s prime minister, Viktor Orbán, to forge a single nationalist Internationale, there are now three rival Eurosceptic rightist groupings instead of the two in the previous legislature. In addition to personal rivalries, these groupings differ over whether to support Ukraine against Russian aggression, as well as over whether to try to transform the EU into a looser grouping of sovereign states or to break away from the union completely. The more “respectable”, pragmatic national conservatives around Italy’s prime minister, Giorgia Meloni, want to keep their distance from more aggressively nativist parties, which advocate expelling immigrants who have acquired citizenship or residence rights. In mid-July, an ad hoc coalition of conservatives, socialists, liberals and Greens united to re-elect Ursula von der Leyen as European Commission president after she made contradictory promises to stick to net zero carbon emission targets, boost industrial competitiveness and ease the regulatory burden on farmers. She is likely to retain the same broad support when she presents her full college of commissioners, nominated by national governments in September, although one or two nominees may well be rejected in the street theatre of confirmation hearings that give the newly elected parliament an opportunity to flex its muscles. The real challenge for Von der Leyen will come when she tries to enact new legislation to enforce sensitive aspects of the European green deal to fight the climate crisis and to protect the environment and biodiversity. Her own conservatives could team up tactically with the far right to vote down measures on nature conservation or pesticides that were bitterly contested in the last legislature. This sort of opportunistic issue-by-issue switch might not amount to a far-right power shift, but it would be more worrying if it extended to making migration policy more inhumane. Such a shift occurred in the French parliament last year, when President Emmanuel Macron’s centrists let the conservative Les Républicains toughen up an immigration bill with discriminatory measures against foreigners that were adopted with the support of the hard-right National Rally (RN), only for it to be struck down by the constitutional council. The result was an emboldening of the RN’s political agenda. In a snap general election in June and July, millions of French people voted tactically for political adversaries rather than let the RN convert its triumphant first-round score into parliamentary dominance. As a result, the National Assembly is deadlocked, with no party or alliance holding a majority. This has weakened Macron’s influence in the EU, but at least the “republican front” firewall has kept the populists at bay for now. It remains to be seen whether France ends up with a centre-right minority government, a minority leftwing New Popular Front administration (less likely), or perhaps an Italian-style technocratic cabinet until fresh elections can be called in a year’s time. While politics takes a summer breather during the Paris Olympics, there is widespread relief that Marine Le Pen’s national populists have been stopped at the gates of power, tinged with foreboding that this may only boost her chances of winning the 2027 presidential election. While the centre is holding at EU level, populist nationalists continue to make inroads in national politics in several parts of Europe. The Netherlands has its first far-right-led ruling coalition, even though the outspoken anti-Islam Freedom party leader, Geert Wilders, was blocked from taking the premiership. Slovakia’s pro-Russian nationalist leader, Robert Fico, whose ally won the country’s presidential election, provides Orbán with backing against EU efforts to toughen financial sanctions over serial abuses of the rule of law in Hungary. In the UK, Keir Starmer’s crushing victory over a Conservative party that lurched to the nationalist right after Britain’s vote to leave the EU showed that populist nationalism can be defeated when voters realise it has failed to deliver on their expectations and left them worse off. However, the recent outburst of violent, anti-immigrant extreme-right riots highlights how a radical fringe, mobilised on social media, can cause political havoc even if its voice in parliament is marginal. The next big test of Europe’s firewalls will come in Germany, when three eastern states hold elections from September that are being watched as a dress rehearsal for next year’s federal election. Despite a series of scandals that led to it being ostracised even by other nationalist parties in the European parliament, the extreme-right Alternative für Deutschland (AfD) is leading in opinion polls in all three states, while the recently created pro-Russian, left-populist Sahra Wagenknecht alliance is credited with up to 20%. Mainstream parties may not win enough seats together to form viable coalitions in any of those states. Of all the events that could change the political dynamics in Europe, the US presidential election is by far the most potent. A comeback for a vengeful Trump would embolden and legitimise European nationalists and populists. Think of the smile on the face of the Reform leader, Nigel Farage, or the red-carpet welcome in Budapest for Orbán’s best buddy. If Harris triumphs, leading an administration embodying diversity, feminism and a strong commitment to the rule of law, it could help strengthen the firewall across Europe. However, barriers to keep the extreme right out of power will only work in the long run if the mainstream parties are able to address the issues with the cost of living, affordable housing and affordable energy that have driven so many voters into the arms of populists on both sides of the Atlantic. Paul Taylor is a senior visiting fellow at the European Policy Centre