WASHINGTON — It’s funny how catastrophe can exaggerate the best and worst parts of ourselves.

In the moments after two airplanes hit the World Trade Center in New York, I managed to stay unusually calm at my desk in the Dirksen Senate Office Building. I called my father, found my sister, and returned frantic press calls until the Capitol Police yelled to get out of the building.

I made more calls from the sidewalk until we were waved away and told to run. I kept returning calls until the phone lines on the East Coast went down as worried people looked for their loved ones.

In those same hours, the House and Senate leadership were whisked away from the Hill to an “undisclosed location.“ For the first time in decades, the succession plan for the country mattered, and the Next Ones In Line had to be accounted for while the rest of the members fended for themselves.

My own boss sat in traffic for four hours trying to get to Arlington. Other senators wandered on the streets and asked CNN reporters doing live shots what was going on. Chaos and control were fighting it out in Washington, but control eventually won out.

By the evening of Sept. 11, the House and Senate leadership of both parties were on the steps of the Capitol holding a press conference together.

Speaker Dennis Hastert, a Republican, promised unity in the face of tragedy. Senate Majority Leader Tom Daschle, a Democrat, spoke next with the same message. “We, Republicans and Democrats, House and Senate, stand strongly united behind the president and will work to make sure that the full resources of the government are brought to bear in these efforts.“

As some members began to cry or walk away, others began to sing “God Bless America,“ and for that moment and in the months that followed, Congress was the best version of itself.

Both chambers were back in session by 10 a.m. on Sept. 12. They remained in session six weeks later when an anthrax attack closed large swaths of the Senate complex for months.

All the while, the House and Senate moved major pieces of legislation quickly to respond to al-Qaida, to overhaul homeland security, and to revamp intelligence sharing.

The results were imperfect, but Congress’ commitment to work together was real and appreciated. By the end of the year, the congressional approval rating jumped to 52 percent, the highest ever recorded since the Gallup poll began in 1974. “Never forget,“ became a constant refrain on and off Capitol Hill. It seemed sincere and even possible at the time.

But 17 years later, Washington seems to have completely forgotten that commitment to work together in defense of the nation. Despite detailed reports about Russian cyberattacks in 2016 and multiple “blinking red“ warnings from President Donald Trump’s own Cabinet that more (and worse) are coming, the House and Senate are still debating each other about whether a threat to the country exists at all.

The urgency of tackling dangers to the United States has given way at the White House to absurdity, self-defense and finger-pointing, while congressional leaders seem mostly focused on their own legacies.

Veteran legislators are throwing up their hands and heading home for retirement while the rest are running like mad to either resist the president or become him.

Campaigns and recesses and fundraising matter enormously to members’ re-elections, but hold no importance for the welfare of the country. Guess where the time and effort are mostly being spent this election year?

The unity that Congress found in the rubble of catastrophe is long gone. It’s been replaced by Republican shoulder-shrugging when asked about mutiny in the ranks of the White House and by made-for-viral moments from Democrats, like when they questioned Brett Kavanaugh in his confirmation hearing last week — only to blast out fundraising emails moments later. From a distance, they all just seem to hate each other. ...

We’re now on the doorstep of a constitutional crisis because Democrats and Republicans spend more time attacking each other as enemies, instead of being allies in the fight against the enemies we know this country is facing. If a catastrophe strikes again, could they rise to meet the challenge? Could these same people be the Congress this country needs instead of what we’ve allowed the institution to become? Do we have to have to wait for something horrible to happen until we find out?

Seventeen years after 9/11, Congress has become the smallest version of itself. It was once so much more than that, but it’s easy to forget.

Roll Call columnist Patricia Murphy covers national politics for The Daily Beast. Previously, she was the Capitol Hill bureau chief for Politics Daily and founder and editor of Citizen Jane Politics. Follow her on Twitter @1PatriciaMurphy.