Philadelphia will post prosecutors in the city on election day to handle voter intimidation claims.

Authorities in Philadelphia will station prosecutors throughout the city on election day to respond to any reports of voter intimidation or other illegal activity after Republican presidential nominee Donald Trump claimed that polling might be “rigged” in this mostly minority city.

Philadelphia is one of many U.S. municipalities wrestling with how to respond to Trump’s call for supporters to “watch” polling places, and corresponding promises from civil rights groups that they will send their own backers to the polls.

“All of our election judges will be provided with cell phones that have direct access to the district attorney’s office of Philadelphia,” said Tim Dowling, chief deputy to City Commissioner Lisa Deeley. “As soon as you cross the line, you’re going to be dealing with law enforcement.”

The Nov. 8 presidential election has been among the most contentious in the nation’s history. Trump, whose campaign has been shaken by allegations that he groped numerous women after a video surfaced in which he made lewd comments about groping women, has refused to promise that he will accept the results of the election if he loses to Democrat Hillary Clinton.

This week, Trump told supporters to “watch” polling places in such cities as Philadelphia, St. Louis and Chicago—all with large minority populations. As Trump has slipped in the polls, he has repeatedly said the election is “rigged” against him.