Iowa Sen. Chuck Grassley is pressing Vanita Gupta, the nominee for the number three position at the Justice Department, over millions of dollars in stock holdings she has in a chemical company that makes a key ingredient that Mexican drug cartels use to make heroin. Gupta holds between $11 million and $55 million in shares of Avantor, a Pennsylvania-based chemical company, according to financial disclosures she has filed with the Office of Government Ethics. Gupta’s father, Raj Gupta, serves as chairman of the board of Avantor. Gupta is the wealthiest political nominee that President Joe Biden has picked while in...