If election violence defines a fragile democracy, a single shocking example of it need not sound a death knell to a vibrant one. But the United States should reflect deeply on Wednesday’s storming of Congress during certification of president-elect Joe Biden’s victory ahead of his inauguration in two weeks. The US still excels in key indices of democracy such as free and fair elections and freedom of speech. But that does not weigh with the radicals in Washington. They remain convinced, the absence of evidence notwithstanding, that President Donald Trump was cheated of re-election. The proliferation of fake news on social media has reinforced their denialism. It would be delusional to think they are outliers among more than 70 million who voted for Trump. Indeed, they may be widely representative of the social, cultural and economic marginalisation many of them apparently feel. Trump’s rise and the anger at his fall reflect the influence of populism, and the potential dangers of it. America’s strong two-party system tends to be polarising anyway. Trump is a populist politician within that system. Scholars believe his populist solutions to complex issues appeal to Americans who feel they have been pushed to the margins of mainstream society and who may as a result have lost faith in its politicians and conventional elites. If there is a lesson in the disturbing scenes it is the risk that marginalisation will leave people feeling unrepresented in the mainstream and vulnerable to populist solutions unlikely to resolve deep-seated grievances. The storming of Congress grates with promotion of the US as a champion of democratic values. Regrettably, Trump incited the rioting, prompting Twitter and Facebook to lock his accounts. World leaders deplored the scenes as “disgraceful”, “saddening” and “horrifying”, with President Emmanuel Macron of France saying the universal idea of one man, one vote was undermined by taking up arms to challenge the result of a legitimate election. Biden has inherited a deeply polarised electorate. His experience as vice-president to Barack Obama, who inherited the aftermath of the global financial crisis, is not directly relevant. But it will fortify him for the mission of reconnecting Americans.