Hunter Biden seemed without a care in the world as he patted backs during the recent state dinner and smiled at the crowds from the White House South Balcony on July 4th. How long, though, can the President and his “teflon son” keep pretending nothing’s unseemly about these spectacles as hostile investigations of Hunter ramp up, and legal woes mount?

The president is reported to be ignoring advice to insulate his presidency from his troubled son, even as Hunter’s devil-may-care July 4 appearance on the White House balcony while cradling his three-year-old son Beau led reporters to ask, again, if the elder Mr. Biden will ever acknowledge Hunter’s illegitimate daughter Navy, age four. The White House, again, would not comment.

America has a long tradition of ogling but tolerating First Family troubles, even having sympathy for presidents who stand by their kin during struggles to see them through. Yet how long will Hunter’s teflon keep protecting him  — and his father — from accountability? What lessons can we learn from presidential history?

President Washington was — as in all things — first. His stepson, John Custis, was a poor student and lazy, but while Washington was a lion on the battlefield, he was a lamb at home, fearing that “in spite of all of the admonition and advice I gave him about selling faster than he bought,” Custis was ruining his life.

After Custis fell short as a delegate to Virginia’s House of Burgesses, the president wrote a note that his stepson might be “little versed” in politics, but even he could show up to sessions on time.

President John Adams called his alcoholic son, Charles, “a madman possessed of the Devil” and disowned him. President John Quincy Adams’ son, George Washington Adams, also fought the bottle, dying by apparent suicide.

President Madison’s hard-living stepson, John Payne Todd, lived up to his middle name. Madison spent a fortune covering his gambling debts without telling the First Lady, Dolley, “to ensure,” he wrote, “her tranquility by concealing from her the ruinous extravagance of her son.”

The press loved President Van Buren’s party boy son, John, and President Theodore Roosevelt’s eldest child, Alice. “I can be president of the United States or I can control Alice,” Roosevelt said. “I cannot possibly do both.”

Hunter benefits from this same brand of understanding; the fact that he’s finally on the mend after multiple trips through rehab seeming to earn him Mr. Biden’s unwavering support. By all appearances sober at last, he’s remarried and living in Malibu with his second wife and young son. 

Americans aren’t so forgiving when the ties that bind are used to exploit high office. People jumped on allegations that President Franklin Roosevelt’s eldest son, Franklin Jr., had cashed in on the family name. The president pushed for another son, Elliot, to get pilot’s wings he hadn’t earned and a promotion, but kept it quiet.

“We’re talking about scandals and about presidential sons being a bit shady,” the author of “Roosevelt Sweeps Nation: FDR’s 1936 Landslide and the Triumph of the Liberal Ideal,” David Pietrusza, told me in our “History Author Show” interview. “Elliot had an aircraft deal with the Soviet Union and Stalin — bombers for a totalitarian regime — and this story gets squashed just before the election. Sound familiar?” 

For Mr. Biden, the threat of impeachment has already been raised after the recent exposure of WhatsApp messages in which Hunter warned that his father was sitting next to him while threatening a business partner in Communist China to send cash.

Whistleblowers have alleged that the attorney general, Merrick Garland, and IRS commissioner, Daniel Werfel, perjured themselves to shield Hunter, and an IRS investigator, Gary Shapley, alleges the agency violated protocol to bend justice for Hunter and slap down a U.S. attorney for Delaware who sought to expand his investigation into the First Son, which Mr. Garland denies. 

During the 1980 election, the Wall Street Journal took an understanding attitude toward President Carter’s reluctance to attack his brother, Billy, who was causing embarrassments with, among other things, his relations with Libya. “He ain’t heavy,” the Journal editorialized at one point. He’s his brother. 

The American public understands and even praises Mr. Biden’s loyalty to Hunter and sympathizes with drug addiction, but if illegalities and cover ups are proven, expect that goodwill to evaporate. Corruption, unlike personal failings, can cut down a president down to size and scratch even a Teflon son.