ARCHIVAL( PRESIDENTIAL DEBATE, C-SPAN, 10-6-20):PRESIDENT DONALD TRUMP: Im urging my supporters to go into the polls and watch very carefully. Thats what has to happen. I am urging them to do it.

ARCHIVAL (NBC, 10-19-20):NEWS REPORT: President Trump has been calling for an army of poll watchers to monitor election sites.

ARCHIVAL (HANNITY, FOX NEWS, 8-20-20):PRESIDENT DONALD TRUMP: Were going to have sheriffs and law enforcement.

ARCHIVAL (MSNBC, 10-1-20):NEWS REPORT: His comments are raising fears about voter intimidation.

ARCHIVAL (NBC, 10-19-20):NEWS REPORT: Theyre worried about the threat of armed men at the polls.

ARCHIVAL (AL JAZEERA):NEWS REPORT: Theres a long history in the United States of poll watching and poll intimidation.

RICK HASEN (PROFESSOR OF LAW AND POLITICAL SCIENCE, UNIVERSITY OF CALIFORNIA, IRVINE): Poll watching, when done right, serves an important function. We want our elections to be transparent. We want to know that eligible voters will not be disenfranchised, that ineligible voters are not being allowed to vote. This is a regular thing in all elections throughout the world The problem is when it crosses the line into intimidation and harassment.

NARRATION: Partisan poll watchers have been part of elections since at least the 1800s, when fraud was common and voting could be a dangerous proposition.

GIDEON COHN-POSTAR (FELLOW, MITCHELL CENTER FOR THE STUDY OF DEMOCRACY, UNIVERSITY OF PENNSYLVANIA): Voting in the 19th century in the United States took place openly. Everyone could see who you were voting for, what ballot you cast. And in that environment, the polls became a really raucous place. Violence and intimidation at the polls ranged from verbal threats, to outright gunplay, stabbings.

NARRATION: New laws ushered in reforms to protect the voting process, like secret ballots and official monitors.

GIDEON COHN-POSTAR: Official poll watchers were appointed to go to the polls and make sure that no fraud and intimidation was taking place. But there was also unofficial poll watching and unofficial poll watching developed very quickly in the 19th century into often a form of voter suppression and intimidation.

NARRATION: After the end of slavery, some states passed laws allowing citizens to challenge a persons right to vote.

GIDEON COHN-POSTAR: Theres one famous case where a group of people, white intimidators, came out to a predominantly black area, stood around the polls with guns and claimed that they were deputy U.S. marshals there to ensure the safety of the polls. And they threatened and scared off about 175 black voters.

NARRATION: Some of the most notorious acts of voter intimidation took place in the 1950s and 60s, as black Americans fought for their voting rights.

Then in 1981, a political scandal broke out when the Republican National Committee sent a ballot security taskforce to predominantly black and latino neighborhoods in New Jersey.

They posted warning signs like this one near the polls.

ARCHIVAL (NEW JERSEY NIGHTLY NEWS, 11-6-81):NEWS REPORT: Allegations that minority voters were intimidated by task force workers have surfaced in several cities.

ARCHIVAL (WNBC, 1981):NEWS REPORT: Republican poll watchers, some of them off duty policemen, wearing guns and armbands, were also near the polls.

ANGELO GENOVA (MANAGING PARTNER, GENOVA BURNS): Do I think its intimidating? From soup to nuts, I think its intimidating and not what our democracy contemplated.

NARRATION: Angelo Genova was a lawyer for the Democrats. They sued for voter intimidation and discrimination, and a settlement required the Republican National Committee to get court approval for future ballot security plans.

ANGELO GENOVA: To me, its heart resided in a provision that made it a violation to engage in any activities that had the effect of deterring African-American voters or Latino voters from participating in elections.

NARRATION: That settlement, or consent decree, was invoked again after other allegations of Republicans intimidating or excluding minority voters. It expired in 2017, making 2020 the first presidential election in 40 years where the Republican National Committee is able to conduct poll watching without court supervision.

ARCHIVAL (MSNBC,10-1-20):NEWS REPORT: The Republican National Committee recruiting some 50,000 poll watchers across the country.

NARRATION: And Democrats are stepping up, too. This year, both parties will send thousands of officially trained and registered poll watchers to monitor the election. They play an important role in keeping the voting process fair flagging any problems and reporting them to officials or party lawyers. And its illegal for them, or anyone, to intimidate voters.

Both parties say their official poll watchers will follow the law, but with political tensions mounting

ARCHIVAL (DAILY MAIL, 10-28-20):TRUMP SUPPORTER: Youre going to vote for Trump whether you like it or not! Youve got no choice!

NARRATION:the rhetoric from the president and his supporters has some experts concerned about another scenario.

ARCHIVAL (DEFEND YOUR BALLOT AD, YOUTUBE, 9-25-20):DONALD TRUMP JR.: We need every able-bodied man, woman to join President Trumps army for election security operation.

RICK HASEN: What concerns me the most when I hear the president make these statements is vigilantes and others who might listen to what the president says, take matters into their own hands. The overall concern is that theres going to be either activities at the polling places which could intimidate minority voters or enough concern that thats going to happen, that it could have a deterrent effect.