The following editorial appears on Bloomberg Opinion.

With less than a month remaining in the presidential campaign, the country faces the specter of a chaotic Election Day. President Donald Trump has urged his supporters to "go in to the polls and watch very carefully" — a suggestion that can be interpreted as a call for greater participation in the long-established practice of election observing, or as an appeal for Trump supporters to stage noisy rallies outside polling places, or both. Whatever the president's intent, election officials should prepare for the worst.

The first priority is for states to enforce existing rules on poll watching, which has been part of the voting process since the birth of the republic. In most states, political parties are allowed to designate equal numbers of representatives to observe in-person voting, report irregularities and check the accuracy of results. Qualification requirements vary by state, but in most cases, poll watchers must be registered voters in the jurisdiction where they serve. Most states limit the number of partisan observers.

Republicans have launched an effort to recruit 50,000 volunteers to serve as poll watchers in battleground states. In August, Trump said his campaign planned to deploy "everybody," including sheriffs, police and U.S. attorneys, to monitor voting sites. Such claims may be fanciful: Trump made similar boasts in 2016, but states reported no increase in people registering to serve as poll watchers. Yet, Trump's (unsubstantiated) claims of voter fraud, have raised the prospect of chaotic scenes that could cause long delays or deter voters from casting ballots altogether.

State election officials should prepare for such disruptions. They should enforce laws that require poll watchers to be certified and vetted before Election Day and impose limits on the number of observers allowed inside voting precincts. Where possible, additional volunteers should be recruited to reduce voting wait times at sites where disputes among poll watchers are most likely to occur. States that ban firearms from voting sites should insist that poll watchers comply. To reinforce local law enforcement, governors should also be ready to deploy the National Guard to places where large demonstrations may impede access to polling sites.

That citizens may require such measures just to safely cast their ballots is unfortunate. But Trump has given ample evidence that he's willing to strip voters of their rights in order to hold on to power. It's up to responsible leaders from both sides to stop him from getting away with it.