The following editorial appears on Bloomberg Opinion.

Thursday's assault on America's seat of government is a stain on the country's history and won't soon be forgotten. The shocking disorder was invited and fomented by a defeated president, not in any plausible expectation that he could hang on to power, but merely to vent his wounded pride. He was enabled by Sens. Ted Cruz, Josh Hawley and others - politicians seeking selfish short-term tactical advantage regardless of the cost to the country they're sworn to serve.

For the Republican Party that Trump has seemed intent on destroying, this is at last a moment for clarity. No more equivocation. No more failing to condemn, let alone actually supporting, a leader who cares nothing for the party or his country. From here on, you stand with Trump and his nihilistic narcissism, or for the possibility of civic government. There's no other choice.

In light of these events, more Republicans are bound to understand what they might only have suspected up to this point - that Trump is not a regrettable necessity, but a clear and present danger to the country. They should bring themselves to put the blame for this disorder where it lies, with Trump and with his enablers. To survive as a viable party of government, Republican leaders must sever their ties with this president. Senate Majority Leader Mitch McConnell's speech opposing the effort to overturn the election was a first belated step in the right direction. Others should follow his lead.

Congress returned to work after control of the Capitol complex was restored and duly affirmed Joe Biden as the next U.S. president. Maintaining order in the capital is the next immediate priority, and a point on which America's politicians should speak and act as one.

Trump made a statement promising an "orderly transition." It would be best if he now said nothing else.

Biden needs to start leading today, before he's inaugurated. He needs to present a face of the Democratic Party that can do business with the many moderate Republicans who voted for Trump reluctantly.

Biden was nominated and elected because he sees his task as uniting a bitterly and closely divided country. With luck, Trump's last disgraceful provocations, and the violence of his angriest and most dangerous supporters, will show the country what's at stake. With luck, they'll help Biden be the president he wants to be.