Border Patrol agents in riot gear take part in a training exercise at the U.S.-Mexico border on Monday in Hidalgo, Tex. (John Moore/Getty Images)

U.S. Customs and Border Protection abruptly canceled a crowd-control exercise it had planned near a Hispanic neighborhood in El Paso on Tuesday after critics raised concerns that the presence of so many armed border agents could discourage voting.

The agency had planned to stage a “mobile field force demonstration” Tuesday morning at the Paso del Norte border crossing, in an area adjacent to a neighborhood known as Chihuahuita with about 100 modest homes.

After lawmakers, activists and the American Civil Liberties Union questioned the decision to conduct the exercise on Election Day, Border Patrol agents said it had been postponed.

The controversy flared as voters began going to the polls in a city where high turnout is especially crucial to the Senate campaign of Rep. Beto O’Rourke, the El Paso Democratic candidate challenging Republican Sen. Ted Cruz.

CBP and Homeland Security officials rejected allegations that the training exercises had any relation to the election.

But Terri Burke, executive director for the ACLU of Texas, said the timing of the crowd-control exercise was “suspicious” and that she welcomed the decision to scrap it.

“We are, obviously, pleased, but it shouldn’t have taken outrage by us, congresspeople and the community for the Border Patrol to know they were being manipulated for political gain,” Burke said.

Texas Secretary of State Rolando Pablos, the state’s chief elections officer, said he called CBP’s director of El Paso field operations about the exercise Tuesday morning and did not see any ill intentions. The exercise would not get “in the way of Texans going to the polls,” said Pablos, a Republican who grew up in El Paso.

El Paso County Republican Party Chairman Adolpho Telles said concerns about the exercise were misplaced.

“It shouldn’t matter. You have no reason to be afraid of law enforcement; you have no reason to be afraid of exercises. The only time the state troopers bother me is when I look at my speedometer and I’m speeding. The rest of the time, it doesn’t bother me,” said Telles, the co-owner of Rosa’s Cantina, the bar made famous in the Marty Robbins’s song “El Paso.”

CBP forces have been conducting exercises in El Paso and other border cities for the past several days in preparation for the possible arrival of a caravan of Central American migrants. On Oct. 29, CBP officers in riot gear briefly closed the Paso del Norte Port of Entry as part of an exercise. Tuesday’s planned exercise, however, is about a quarter-mile west of the port and near the residential neighborhood.

O’Rourke was told of the exercise plan during a news conference just before his final campaign rally Monday night at the University of Texas at El Paso.

“No walls, no CBP exercises [are] going to keep us from honoring our laws, our commitments,” he said. “Why this is happening now, why the president is stirring these issues up at this moment with 24 hours before we decide this election, I’ll leave that to you to conclude,” he said.

Julián Castro, the former housing and urban development secretary in the Obama administration and a potential 2020 Democratic presidential candidate, said the planned exercise demonstrated the Trump administration’s “callousness.”

“While I’m glad to see that they’ve postponed it, it really calls into question whether these folks are playing games to try to chill the vote,” said Castro, who was in El Paso on Tuesday to campaign for O’Rourke and attend his election-night party.

Nick Miroff in Washington contributed to this report.