House Democrats staged a sit-in June 22 for more than 15 hours to try and force a vote on gun control measures. Here's why. (Victoria Walker/The Washington Post)

Thomas E. Mann is a senior fellow in governance studies at the Brookings Institution, a resident scholar at the Institute of Governmental Studies at the University of California, Berkeley and co-author of “It’s Even Worse Than It Looks.”

Sometimes civil disobedience is justified. Sometimes it is necessary. The unprecedented events playing out on the House floor — Democratic members staging a sit-in in the well of their own chamber — represent such a moment.

The immediate, and understandable, precipitating events were the massacre in Orlando and the refusal of House Republican leaders to permit a vote on a measure to try to keep lethal weapons out of the hands of possible terrorists and others whose past behavior and mental state mirror the profile of the mass murderers who have made the United States the citadel of gun violence.

But the underlying cause for the revolt runs far deeper. Partisan polarization and intense competition for control of Congress have ushered in a ruthless stewardship of the first branch of government, motivated mostly to kill bills and avoid votes, all in the quest to retain or gain majority control. Regular order did not carry the day in the House, but then regular order has not been in evidence in the House or Senate for many years.

No action of consequence on the central issues of the day is possible under divided party government. And no party is held to account for its willful obstruction. The public sees an undifferentiated blob of venality and haplessness — Congress, Washington, the establishment — and remains without a clue as to what is wrong and what can be done about it.

Senate rules offer certain safety valves to allow lawmakers to vent their frustration with this situation — to wit, the filibuster waged by Senate Democrats last week to demand votes on similar measures. Party-line voting and a supermajority hurdle took those bills down, but at least every senator was on record months before the 2016 election.

House rules offered Democrats no comparable means to demand a vote, so they improvised. The idea came from one junior member but spread through the party caucus like wildfire. Those of us watching from outside were transported back to the moral power, determination and possibilities of the civil rights movement.

The sit-in is a bracing and potentially consequential diversion from the contemporary norm. It is disruptive but civil and nonviolent. No individual outbursts of hatred and anger, no conspiracy theories — just a plea for common sense on a matter of signal importance to the country and an opportunity for democratic accountability. The media now has a story other than the presidential horse race, one that might actually resonate with regular folks.

Nothing may come of this. The safest bet is always against Congress passing gun control legislation. But this time may be different. The agenda is modest: keeping automatic weapons out of the hands of those who should not have them. It is well short of the ambitious agenda passed (to the Australian public’s great benefit) by a conservative Australian government in 1996 in the aftermath of a mass killing. Public support is unusually high. Civil disobedience has heightened its salience. Republicans know they are holding a weak hand in the election, one the National Rifle Association cannot strengthen. Sixty votes in the Senate, 218 in the House are not beyond reach. If not this year, maybe next.