The world’s foremost power and oldest democracy lost control of its own capital on Wednesday. The storming of the US legislature by a rightwing mob suspended its business, forced elected politicians into hiding and, while details remain scarce, cost lives. American institutions have come under attack before. Never, though, at the instigation of its own president. As mayhem spread, Donald Trump did not categorically deplore the violence he helped to unleash from his own supporters. Some of his lawmakers then challenged the certification of Joe Biden as his successor, on the same specious grounds that incited the riot. An event can be shocking and entirely predictable all at once. To suggest that this one has been coming since November when Mr Trump contested his election defeat is to understate the case. Even before polling day, he implied that any loss would be down to electoral fraud. And for years before that, he had encouraged the wildest elements of the right through gesture and insinuation. It is tempting to regard Wednesday as the culmination of his incendiary political career. Despite Mr Trump’s belated pledge early on Thursday of an “orderly transition”, with two weeks still to run of his presidency things may yet deteriorate. It is up to Congress, other members of his administration and above all the Republican party to avert that fate. Options that were exotic at the start of the week are now common currency in Washington discourse. One is to exercise the 25th amendment of the Constitution, which allows for the removal of an “unable” president. Mike Pence, the vice-president, would then see out the remainder of the Trump term. Another course is to complete the unfinished business of a year ago. Mr Trump was impeached for crimes relating to foreign meddling in the 2016 election, but then acquitted in the Senate. Many Democratic lawmakers now suggest another attempt over his part in Wednesday’s turmoil. The hope is that enough Republican senators will find their conscience to form a supermajority for conviction. Impeachment has the advantage of barring Mr Trump from another run at the presidency. Neither approach guarantees order. Each would increase the far-right’s baseless sense of dispossession. Mr Trump does not even need a formal office from which to inflame them. Ideally, public outrage at the assault on Capitol Hill would cause agitators to calm down or even rethink. This would allow the nation to make it through to Mr Biden’s inauguration on January 20. It is no longer prudent, however, to count on such luck. Unfit for office in the first place, Mr Trump is becoming more dangerous, not less, with time. And there is too much of it left to simply wait him out. Of the flawed options available, the least bad is to commence impeachment proceedings. Even if it fails, it would at the minimum send a moral signal. The raid on the seat of US democracy confirmed what should have been obvious years ago. America has a national security problem in the form of the far-right. This closed world of misinformation, paranoia and grievance receives succour from mainstream conservatives: public office-holders, cable news anchors. The costs are increasingly unmistakable. Overlaying the domestic threat is the geopolitical ignominy. China will never find it easier to mock democracy as a charter for chaos. Even Turkey tweeted its concern for America’s civic peace. Shoring up its democracy, and therefore its good name in the world, will take the US years of work. It can start with formal action against a rogue president. A man who despaired of “American carnage” has incited another kind. He cannot be allowed to cause more.