Allen H. Weisselberg, for decades one of Donald J. Trump’s most trusted executives, has reached a deal to plead guilty on Thursday and admit to participating in a long-running tax scheme at the former president’s family business — a serious blow to the company that could heighten its risk in an upcoming trial on related charges. Mr. Weisselberg will have to admit to all 15 felonies that prosecutors in the Manhattan district attorney’s office accused him of, according to people with knowledge of the matter. And if he is called as a witness at the company’s trial in October, he...
