PEOPLE who worry about Donald Trump’s presidency worry especially about how he might respond to a national-security crisis. Now they know. American intelligence chiefs have long viewed Russia’s campaign to discredit and influence America’s elections as a security threat. And the 16 indictments unveiled by Robert Mueller, the special counsel in the case, imply that the threat is more long-standing, sophisticated and effective than was commonly understood. Such clear evidence of foreign interference would normally constitute a moment for the commander-in-chief to reassure an anxious nation that the attack—in an election year, no less—would be repulsed. But that was not Mr Trump’s response.

The president made no formal comment on the indictments, yet his Twitter feed suggested they stirred in him a range of powerful emotions. He at first rejoiced that Mr Mueller had not accused him of complicity in the Russian sabotage: “The Trump campaign did nothing wrong—no collusion!” Then he fretted that it was getting so much attention as to cast doubt on his legitimacy. In subsequent tweets the president lambasted the FBI for spending too much time investigating the attack. It could otherwise have prevented a recent massacre of schoolchildren in Florida, he wrote. He then attacked his national-security adviser, H.R. McMaster, for failing to defend him more robustly and Barack Obama for failing to stop the Russians sooner. He claimed never to have dismissed the Russian campaign as a hoax, though he has done so many times. At no point did Mr Trump express any concern for the safety of American democracy.

This was so remiss as to suggest to some that he had just broken his presidential oath, to “protect and defend the constitution”. It more obviously illustrated the mundane ways in which Mr Trump is himself undermining the country’s democracy, by transgressing the unwritten rules which America, like all mature democracies, has developed to oil the wheels of its governing arrangements and limit the potential for discord. Important presidential norms previously included, for example, civility, respect for the rule of law, paying lip-service to the truth and not trying to extract political advantage from massacres of children. Mr Trump dispensed with that lot in a few tweets. Meanwhile, the failure of so many Republican politicians to criticise his poor behaviour points to another concern. It argues the damage Mr Trump is doing could be enduring.

Until his political advent, norms were rarely discussed outside academic circles. Americans took them for granted. These days Trump-worriers debate them endlessly. “Like oxygen or clean water, a norm’s importance is revealed by its absence,” write two Harvard professors, Steven Levitsky and Daniel Ziblatt, in a new book, called “How Democracies Die”. They consider two norms most important. One is mutual tolerance, or a willingness to accept competitors as legitimate rivals. The other is forbearance, or an acceptance by politicians of the need to exercise their powers judiciously, to avoid needless confrontation.

Much of Mr Trump’s bad behaviour falls foul of the first norm. The president considers any rival, at times including the institutions over which he presides, an enemy to be obliterated. He has meanwhile been somewhat restrained. Though he sacked his FBI director, James Comey, which helped trigger Mr Mueller’s investigation, he has not sacked Mr Mueller, as he would like to do.

There is hope, not least because America’s political traditions have survived powerful rule-breakers before. Franklin D. Roosevelt tried packing the Supreme Court in his favour. Senator Joseph McCarthy assailed Americans’ civil liberties and their credulity. Richard Nixon was a crook. Surveying America’s political history, Larry Diamond of Stanford University divines “a general pattern of resilience, punctuated by dark periods of authoritarian temptation.” Indeed the two are related; America’s democracy has tended to emerge stronger after each moment of testing. After Roosevelt, the Supreme Court’s independence was affirmed; after Watergate, Americans embraced transparency. To some degree Mr Trump’s rule-breaking is likely to have a similar effect. A handful of states are already mulling new laws to require prospective presidential candidates to publish their tax returns, which would take care of one of his most notable norm-transgressions. Yet in one sense, at least, this dark period looks much gloomier than its recent precursors.

Unrestrainable and unimpeachable

America has not been so intensely polarised by party since the aftermath of the civil war. This is the essential context for Mr Trump’s rule-breaking, and the reason why this time might be different. Ever since Newt Gingrich turned politics into war in the 1990s, the Republicans have sought to delegitimise and stymie their opponents. By slandering Barack Obama as a Muslim Marxist they inspired Mr Trump to question his place of birth, by rubbishing climate scientists they prepared the way for the president’s wider assault on truth and reason. Egged on by the vituperative conservative media, even some Republicans who disapprove of Mr Trump are wedded to such tactics. There is no obvious reason why they would abandon them after he moves, or is moved, on.

And that might not be for some time, because of the other advantage partisanship affords him—the implacable support of his party. Few Republican congressmen decried Mr Trump’s response to Mr Mueller’s indictments. Their voters would defenestrate them if they did. By the same token, Mr Trump is probably fretting about the special counsel too much. Whatever dirt he finds, there is little chance of Republican lawmakers abandoning Mr Trump as they abandoned Nixon. If he is defeated, it will be at the polls. Which is another reason why Mr Trump’s failure to take steps to prevent meddling is so worrying.