Drew Brees and the Saints overpower Tony Romo and the Cowboys at the Superdome. New Orleans set an NFL record with 40 first downs. (John David Mercer/USA Today Sports)

It was around the time Al Hirt’s voice came blaring over the loudspeaker for the fourth rendition of “When the Saints Go Marching In” of the first half that it became apparent what was going on at the Superdome on Sunday night. This was going to be one of those games, the kind that has come to define the Drew Brees era, where he could hand off to anyone he wanted or throw it to any part of the field and nobody was going to stop him or the New Orleans Saints.

Certainly the Dallas Cowboys were not. In what might have been a compelling showdown of first-place teams, one team looked like a Super Bowl contender and the other looked like a candidate for an offseason overhaul. With Brees moving the ball up and down the field at will, the Saints set an NFL record with 40 first downs, set a franchise record with 625 total yards and romped to a 49-17 win in front of 73,018 fans.

We were extremely efficient on offense, both with the run and the pass,” Brees said. “When you have numbers like that — obviously, that doesn’t happen too often.”

While the Saints remained a game ahead of Carolina in the NFC South standings, the NFC East continued to collapse into itself, a black hole of mediocrity. The Cowboys’ loss, coupled with the Philadelphia Eagles’ win earlier in the day, have the two teams tied atop the division standings at a robust 5-5, 11 / 2 games better than the New York Giants, who won their third straight Sunday, and the Washington Redskins.

The Cowboys are loaded with superstars, but on a night like Sunday, when all of them are neutralized, injured or indifferent, they can look downright awful. Just to name a few: Defensive end DeMarcus Ware was still hobbled by the hamstring injury that had kept him out the previous three weeks. Quarterback Tony Romo was strangely ineffective from the beginning. Wide receiver Dez Bryant didn’t even have a pass thrown to him — let alone catch one — until early in the third quarter.

The Post Sports Live crew discusses the suspension of Miami Dolphins guard Richie Incognito and why his racist and threatening text messages to teammate Jonathan Martin are not typical NFL hazing. (Post Sports Live/The Washington Post)

“It’s embarrassing to not be representative [and] not be competitive,” Cowboys owner Jerry Jones said.

Brees, meanwhile, was on his way to one of those epic games — the kind he produces more than any other quarterback in the league. Every time he threw, it seemed, there was green space around him in the pocket and even more green space around his wide-open receiver. At one point, he completed 19 straight passes, tying a personal best, as the Saints opened up a 28-10 halftime lead — at which point they had more first downs (21) than the Cowboys had offensive snaps (20).

The game would get interesting again only once after that, when the Cowboys scored late in the third quarter, pulling to 35-17, then recovered a surprise onside kick. But the Cowboys, aided by a crippling intentional-grounding call on Romo, went three and out. The Cowboys finished the game 0 for 9 on third-down conversions, while the Saints were 9 for 12.

The Cowboys seemed determined to run the ball Sunday night — after a week of angst at Valley Ranch over the fact they had rushed only nine times, a franchise low, in a narrow win over Minnesota the week before — handing off to running back DeMarco Murray on eight of their 11 offensive plays in the first quarter. The idea, aside from achieving some sense of offensive balance, was to chew up clock and keep the ball out of Brees’s hands as much as possible.

At one point on the Cowboys’ long touchdown drive that spanned the first and second quarters, they handed off to Murray five straight times — one of them a 35-yard burst off left tackle — to move to the New Orleans 7-yard line. From there, they attempted a pass — incomplete — then gave it again to Murray, who went in for the score.

But that pretty much ended the competitive portion of the game. After a punt on their opening drive, the Saints went on to reel off four consecutive touchdown drives, with Brees looking more unstoppable on each one. The Saints compiled nine different offensive plays of 20-plus yards, three of them on rushes by Mark Ingram, who gained a career-high 145 yards on the ground.

“There’s still so much more we can improve on,” Ingram said. “We plan on playing a lot bigger games than this one.”

By the fourth quarter, with Brees closing in on 400 yards — which would have made him the fifth quarterback to hit that mark this season against the Cowboys’ porous defense — the Saints apparently decided, just for the heck of it, to see whether they could put together a long touchdown drive with nothing but handoffs. And of course, they could. Ingram and Pierre Thomas shared the eight carries on the drive, with the latter blasting it into the end zone from the one.

Here came the rhythmic handclapping and Hirt’s tenor over the loudspeakers for a seventh time, the Saints, on this night, having marched in every which way there is.