It's hard to rank all the dangerous and disturbing things that Donald Trump has said during the presidential campaign. But his Aug. 12 call in Altoona, Pennsylvania, for volunteer "election observers" to monitor voting in certain Democratic precincts has to be on the list somewhere.

"The only way we can lose, in my opinion — I really mean this — in Pennsylvania, is if cheating goes on," Trump said. He continued: "We have to call up law enforcement. And we have to have the sheriffs and the police chiefs and everybody watching" on Nov. 8.

Then he invited his supporters to help, saying, "I hope you people can sort of not just vote on the 8th, go around and look and watch other polling places, and make sure that it's 100 percent fine."

The next morning, Trump's campaign website featured a form where voters could "Volunteer to be a Trump Election Observer." It seems to be just a fundraising ploy: As soon as you sign up, you're directed to a donation page. Or it could be a new twist on an old — and illegal — form of voter intimidation. Or both.

In 1981, the Republican National Committee unveiled its "National Ballot Security Task Force," hiring off-duty New Jersey cops to stand around minority precincts on Election Day. Democrats sued, and in 1982 the parties agreed to a federal consent decree that bans such voter intimidation tactics. The consent decree was to expire next year. Trump's Altoona speech could mean it will be renewed.

Pollsters say Pennsylvania's 20 electoral votes are vital for a Republican victory. The state has gone Democratic in every presidential election since 1992, and most recent polls show Hillary Clinton with at least a 10-point lead in the Keystone State.

But Trump's ego will not accept that. In his thinking, the surveys must be rigged, and thus the election will be rigged, too. By casting doubt and mistrust on the democratic process, he undermines it.

Pennsylvania Republicans know full well the demographic changes that have turned their state blue in national elections. That's why in 2012 they passed a voter-identification law requiring photo IDs to vote. The only chance to win was to suppress the growing black and Hispanic vote, as Republican state Rep. Mike Turzai inadvertently admitted when he boasted that voter ID "is gonna allow Gov. (Mitt) Romney to win the state of Pennsylvania."

Romney lost by five points. In 2014, a state judge threw out the Pennsylvania voter ID law, saying there was no evidence of voter fraud.

Now comes Trump, who doesn't need evidence to make scurrilous charges and who appears to be summoning the dark forces of paranoia and intolerance to his own ends. His list of horribles grows ever longer.

REPRINTED FROM THE ST. LOUIS POST-DISPATCH