Joe Biden’s campaign and other Democrats in key battleground states say they’re readying their own efforts to monitor balloting as they express concern about President Donald Trump’s call for supporters to show up at the polls to watch for problems with voting.

Biden's campaign has enlisted thousands of volunteers and the Democratic National Committee began building voter-protection teams in some states as early as last year, according to the campaign.

"I think we feel like we have the right team in place and the right plans in place," said Rachana Desai Martin, Biden's national director of voter protection.

Republicans have plans to use about 50,000 volunteers from early voting through Election Day, according to the Republican National Committee, and Trump is actively encouraging supporters to sign up to be a "Trump Election Poll Watcher" as part of the "Army for Trump."

"I'm urging my supporters to go into the polls and watch very carefully," Trump said during Tuesday's debate with Biden. "Because that's what has to happen. I am urging them to do it."

Trump said early Friday that he has tested positive for coronavirus along with his wife, Melania, and one of his closest aides, Hope Hicks. It's unclear how that will affect his campaign one month before the election.

The president's statements raised concerns among election lawyers and voting-rights advocates about potential voter intimidation or clashes. There have already been scattered confrontations, including on the second day of early voting in Virginia on Sept. 19, and on Tuesday in Philadelphia with the opening of satellite election offices.

There are a number of third-party groups that are recruiting either off-duty or retired law enforcement or military who may show up as so-called ballot security task forces, said Adam Sparks, an election lawyer with Krevolin and Horst in Atlanta.

"I'm concerned about physical intimidation at the polls," said Sparks, who is part of a team of Democratic lawyers opposing Republican efforts to restrict voting.

In Philadelphia, the Trump campaign is suing the city for access to satellite election offices that were opened this week. On Tuesday, a deputy sheriff escorted Trump's Pennsylvania director of Election Day operations out of an office when election officials said he was being disruptive, Politico reported. A Trump campaign lawsuit also challenged a commonwealth law that requires poll watchers to live in the county where they observe the polls.

While Trump complained during Tuesday’s debate that poll watchers were denied access because “bad things happen in Philadelphia,” city commissioners said no poll watchers were certified yet — and that by law, they can only observe polling places on Election Day.

In Pennsylvania and most other states, a limited number of poll watchers representing candidates and political parties must be approved to enter polling locations and observe the process, and they can't interact with voters.

There's concern about the potential for clashes and problems at the polls, but it's illegal to intimidate or harass voters, said Suzanne Almeida, interim executive director of Common Cause Pennsylvania. The group is helping lead a coalition with about 1,000 nonpartisan "poll monitors" who will be outside polling locations across the commonwealth to ensure voting goes smoothly.

"We are doing a lot scenario planning," Almeida said. "The best thing we can do is prepare in advance."

In Ohio, the state Democratic Party launched what it called its "most robust voter-protection program ever" starting before the state's primary this year and has been working for months to prepare for early voting and Election Day by recruiting poll observers across the state, Chairman David Pepper said.

Pepper said it's "troubling" that Trump is urging his supporters to go to the polls to watch because of fears about voter intimidation.

Democrats are especially concerned about the lapsing of a 1982 federal consent decree requiring the Republican National Committee to get court approval before undertaking certain efforts to prevent voter fraud. The decree was issued after a federal court was told the RNC enlisted the help of off-duty sheriffs and police officers to intimidate voters by standing at polling places in minority precincts.

"In the past there has been a lot of bluff and bluster," Myrna Perez, director of the Voting Rights and Elections Program at the Brennan Center, a nonpartisan law and policy institute, said in an interview. "We have more reason to take it seriously now."

The RNC says the decree's 2017 expiration puts the party on an equal basis with Democrats.

"Now that the playing field has been leveled, we can do what Democrats and other Republican groups have been able to do for decades: ensure that all votes are counted properly, and that more people can vote through our unmatched field program," said RNC spokesman Mike Reed. "This is about getting more people to vote, certainly not less."

Reed rejected suggestions poll watching will be harmful. Poll watchers will "receive rigorous training to abide by each state's laws for observing the voting process," he said. "We make very clear to volunteers they need to be respectful and polite, and are not there to be intimidating."

In Florida, no new measures are being enacted because of Trump's remarks during the debate, said Hillsborough County Supervisor of Elections Supervisor Craig Latimer, who's also president of the Florida Supervisors of Elections. Poll watchers are common in elections, and they must follow credentialing and other rules, he said.

Poll workers who see problems developing at polling places are trained to alert law enforcement and the supervisor's office, Latimer said.

The Wisconsin Republican Party has used poll watchers for years to identify legal issues and ensure compliance for a smooth election process, and "we'll continue that practice this cycle," spokesman Alec Zimmerman said by email.

New York State Board of Elections Republican Co-Chair Peter Kosinski said he's "not really concerned about that kind of activity here.

State law allows both major parties to have volunteer poll watchers at polling sites, and New York also has two Republican and two Democrat poll inspectors to ensure nothing wrong is going on, Kosinski said.

"I have full confidence that those poll workers, those inspectors, are able to handle themselves at the poll sites," he said.

The poll watchers can challenge voters, and the inspectors would then make the final determination as to whether there is a problem, he said.

The state has sufficient staffing and resources to “ensure that the poll sites are open, accessible, and that everybody’s rights are being protected,” he said.