The Cowboys missed a field goal that would have forced overtime as time expired. (John McDonnell/The Washington Post)

A debatable snap-infraction penalty on a would-be game-tying field goal attempt by the Dallas Cowboys on Sunday at FedEx Field helped spell the difference for first place in the NFC East.

With the Cowboys trailing the Washington Redskins by three points and lining up for a 47-yard field goal attempt by kicker Brett Maher in the closing seconds, the Redskins appeared to jump offside. But Cowboys long snapper L.P. Ladouceur was called for the snap infraction.

With the Cowboys pushed back by five yards, Maher sent his 52-yard kick off the left upright. The Redskins won, 20-17, to secure the division lead.

“I never had that before,” Ladouceur said. “I do the exact same thing every time. That’s what I was telling the refs: I do the exact same thing.”

Maher’s hooking kick, it seemed, would have been good from five or 10 yards closer. But he refused to blame the penalty.

“Not at all,” Maher said. “That penalty had zero impact on the result of that kick. I can promise you that.”

Ladouceur is a 14-year NFL veteran who said he had seen that call made in the league “not very often” over the years.

“They told me that I was the one responsible for the false start,” he said. “I did the exact same thing I usually do. . . . Bad turn of events there. . . . I’m not trying to get him offsides. I know the situation.”

The loss dropped the Cowboys’ record to 3-4. They’re tied with the Philadelphia Eagles for second place behind the division-leading Redskins, who are 4-2 after the win.

The Dallas offense spent much of the day running — and throwing — in place. Tailback Ezekiel Elliott was bottled up by the Washington defense, running for only 33 yards on 15 carries. And there were not enough offensive alternatives for the Cowboys. Their first touchdown came on a long pass from quarterback Dak Prescott to rookie wide receiver Michael Gallup late in the first half. But Prescott lost two fumbles, one of which gave the Redskins the touchdown that seemed to seal the outcome.

The Cowboys added a one-yard touchdown dive by Prescott in the final two minutes, then got the ball back and drove to Maher’s missed field goal.

Prescott threw for a respectable 273 yards on 22-for-35 passing. But with Elliott such a nonfactor, the Dallas offense was not quite up to the task.

The Cowboys were coming off a 40-point performance in a victory at home over the Jacksonville Jaguars. Still, their offensive production has been the issue most of the season. Elliott generally has thrived, but the passing game has struggled after tight end Jason Witten retired and joined ESPN’s “Monday Night Football” broadcast booth and the team parted ways with wide receiver Dez Bryant.

The lack of playmaking, game-breaking abilities among Prescott’s receivers led to a report by ESPN earlier Sunday that the Cowboys are exploring a trade for Oakland Raiders wideout Amari Cooper.

“In a trade, it takes two,” Cowboys owner Jerry Jones said in a pregame radio interview. “You have to take a look at the areas of really alleged need.”

For most of Sunday’s game, the offensive performance did little to alleviate the concerns about Prescott and the passing game. With Elliott limited to 13 first-half rushing yards, the Cowboys could not come up with a Plan B. They were held scoreless until late in the first half.

Prescott was taken to the medical tent on the Cowboys’ sideline after absorbing a shoulder to the head by Redskins cornerback Greg Stroman at the end of a run. It was a legal hit since Prescott was a runner at the time. Prescott was cleared and returned to the game without missing a play.

The Cowboys’ only first-half offensive competence came when Gallup beat Stroman deep along the left sideline and hauled in Prescott’s on-target throw for a 49-yard touchdown a minute before halftime. That tied the score at 7. The Cowboys fell behind on a pair of second-half field goals by the Redskins. But Maher’s 47-yard field goal narrowed the deficit to 13-10 with a little less than 10 minutes remaining.

Otherwise, there was frustration for the Cowboys. A holding penalty on rookie guard Connor Williams negated what would have been a key fourth-quarter completion from Prescott to wide receiver Cole Beasley for a first down. On the next play, Prescott was hit by linebacker Ryan Kerrigan and lost the football, which was scooped up by the Redskins’ Preston Smith for a touchdown.