A mostly efficient performance by quarterback Robert Griffin III went to waste amid a flurry of second-half penalties, dropped passes and yet another special-teams misadventure as the Washington Redskins somehow reached a new low point. They lost to the New York Giants, 24-17, on Sunday night at FedEx Field in a game that ended with a furor over what down it was as the Redskins’ last-gasp drive fizzled.

The Redskins squandered a two-touchdown lead in the first half and lost their fourth straight game. Their record plummeted to 3-9, and they officially were eliminated from NFC playoff contention. They have a firm grip on last place in the NFC East, now two games behind the third-place Giants, who are 5-7 after beginning the season 0-6.

“When you’re out of it, it’s very disappointing,” Redskins Coach Mike Shanahan said. “Now you find out how guys step up and they play the remainder of the season. You don’t like to play for pride. But sometimes that’s the card that’s dealt, and that’s where we’re at right now.”

Griffin completed his first 12 passes. He went 16 for 17 in the first half en route to a 24-for-32, 207-yard passing performance. He also ran for 88 yards. The Redskins crafted a 14-0 lead on tailback Alfred Morris’s first-quarter touchdown run and Griffin’s second-quarter touchdown pass to tight end Logan Paulsen.

But the Redskins again came undone. The Giants got even by halftime on a touchdown run by tailback Andre Brown and quarterback Eli Manning’s touchdown pass to tight end Brandon Myers. The Redskins came unglued thereafter with unsportsmanlike conduct penalties on wide receiver Santana Moss and cornerback DeAngelo Hall, a five-yard penalty on wideout Pierre Garcon for kicking the football off the turf after a play and a botched snap on a punt by long snapper Kyle Nelson.

The Washington Post's Mike Jones analyzes what's in store for the Redskins when they take on the Kansas City Chiefs on Sunday. (Mike Jones & Sandi Moynihan/The Washington Post)

Brown’s second rushing touchdown of the game followed the bad snap, and the Giants held on from there as the Redskins’ only second-half points came on a field goal by place kicker Kai Forbath. Their final drive ended when Garcon had the ball taken from him by safety Will Hill after a fourth-down completion. That came after confusion over whether the Redskins had gotten a first down previously on that set of downs.

Shanahan said he was told by an official after the Redskins’ second-down play that they had gained a first down. A set of chains also were moved as if the Redskins had a first down.

“I told him I wanted a measurement because I knew it was close,” Shanahan said. “It was inches. And he said, ‘No, it’s a first down.’ And he moved the chains. And then after I saw it was fourth down, I asked him, ‘You already told me it was first down.’ . . . So it was quite disappointing.”

Referee Jeff Triplette told a pool reporter: “I feel like we signaled third down. The stakes just got moved incorrectly.”

Linebacker Brian Orakpo had two sacks for the Redskins, but Manning connected on 22 of 28 passes for 235 yards.

The Redskins were playing their second straight nationally televised game thanks to the decision by NBC and the NFL not to switch to a different game for the Sunday night telecast under the sport’s flexible scheduling plan. They scored a touchdown on their opening offensive possession of a game for the first time this season. With rookie tight end Jordan Reed on the inactive list for a second straight game since he suffered a concussion, Griffin turned to forgotten-man tight end Fred Davis for a key third-down catch on the opening drive. The 12-yard completion, Davis’s first catch since Sept. 15, gave the Redskins a first down at the New York 2-yard line. Morris scored on a second-down carry from the 1.

“We were really jelling early on, putting points up, able to move the ball really well,” Griffin said. “And then in the second half, we just shot ourselves in the foot, got in some bad situations.”

Griffin’s 19-yard touchdown throw over the middle to Paulsen on a third-and-nine play upped the Redskins’ lead to 14-0 in the second quarter. The Giants had appeared relatively disinterested in the proceedings to that point. But they got their running game going on their way to Brown’s 23-yard touchdown dash. The Giants got even 35 seconds before halftime when the Redskins left Myers open in the middle of the field. The tight end caught Manning’s on-target throw for a 22-yard touchdown.

The Redskins began unraveling in the third quarter when Moss was penalized for holding and unsportsmanlike conduct on the same play, stalling a drive. But Manning’s high throw resulted in a tipped-pass interception by Redskins safety Brandon Meriweather. The offense took over at the New York 12-yard line but went three yards backward thanks to the five-yard delay-of-game penalty on Garcon for kicking the football in frustration after Griffin’s third-down incompletion. Even so, Forbath delivered on a 33-yard field goal.

“The penalties were something we have to address,” Orakpo said. “It’s very disappointing when we continue to get penalties and shoot ourselves in the foot.”

The Giants took the lead on Brown’s one-yard touchdown in the opening minute of the fourth quarter. The touchdown was set up by Sav Rocca’s deflected 18-yard punt for the Redskins after the snap was rolled back toward him by Nelson.

“I heard something, and I just shouldn’t have snapped it,” Nelson said. “I should have waited. Worst-case scenario, we take a delay of game or a false start or something. That’s what I should have done.”

Hall was penalized for unsportsmanlike conduct during the Giants’ drive. The Giants added a 39-yard field goal by place kicker Josh Brown with just more than 21 / 2 minutes to play.

“You can’t lose your poise,” Shanahan said. “That was disappointing. We’ve got some competitors out there. . . . We’ve got to keep our poise in those situations, and we lost it a couple times.”