Year after year, in shutdown fight after shutdown fight, in debt-limit standoff after debt-limit standoff, you could count on this: While Republicans would be bickering and taking potshots at each other, Democratic leaders would stay in lockstep — giving their members a united front to rally behind. That all exploded in dramatic fashion this week, culminating Friday at a news conference unlike any I have seen in my career covering Congress, where the No. 1 House Democrat repeatedly dodged questions about whether the No.

1 Senate Democrat was fit to lead. Should Senate Democrats ditch Chuck Schumer? House Minority Leader Hakeem Jeffries, as the kids say, chose violence: “Next question.” It was the diss heard around the Capitol and in Democratic circles around the country.

It marked the end of decades of relative peace atop the Democratic ranks and exposed the friction between two Brooklyn natives who had worked closely together last year to engineer a new presidential ticket. And it sent a worrying signal to their party: In the future, these two leaders won’t necessarily be singing from the same political hymnal. The stunning breach comes just as President Donald Trump takes a wrecking ball to the federal bureaucracy and pushes the limits of his constitutional powers.

And yet the Jeffries-vs-Schumer drama has emerged as the biggest show on Capitol Hill this week — a distraction for Democrats that is yanking the headlines away from Trump’s tough polling and a spiral.