During Grover Cleveland's second term, in the 1890s, the White House deceived the public by dismissing allegations that surgeons had removed a cancerous growth from the President's mouth; a vulcanized-rubber prosthesis disguised the absence of much of Cleveland's upper left jaw and part of his palate.
As for Vietnam, what matters is that Kennedy successfully resisted pressure to send anything more than military advisers, a stance that was a likely prelude to complete withdrawal from the conflict. There is solid evidence of his eagerness to end America's military role in that country's civil war.