Throughout the 15 months he’s been running for president, Donald Trump’s campaign has paid private security contractors at least $432,201 for protection—$320,453 of which was spent after he was given a Secret Service detail in November 2015, according to Federal Election Commission filings.

The calculus for Trump seems simple. A public figure since the 1970s, he’s long had reason to take precautions when it comes to his safety. And now, as perhaps the most divisive major party nominee in American history, there’s more cause for concern than ever. Not to mention that being surrounded by macho former law-enforcement officials adds to Trump’s tough guy mystique.

But the size and scope of his outside security operation comes with its own set of complications and risks. He is the only nominee to be insulated by a staff of his own security and the Secret Service simultaneously, a potential cause for conflict in the ego-filled world of armed musclemen. And it’s unclear if the campaign is abiding by federal campaign-finance laws by using its funds to pay security personnel who, before his candidacy, were on the Trump Organization payroll.

“It is unprecedented,” said one high-level official with knowledge of the Secret Service machinations. “The apparatus surrounding Mr. Trump is extensive to the point of looking dysfunctional.”

And the dysfunction is glaring....