WACO, Texas — Former President Donald J. Trump spent much of his first major political rally of the 2024 campaign portraying his expected indictment by a New York grand jury as a result of what he claimed was a Democratic conspiracy to persecute him, arguing wildly that the United States was turning into a “banana republic.” As a crowd in Waco, Texas, waved red-and-white signs with the words “Witch Hunt” behind him, Mr. Trump devoted long stretches of his speech to his own legal jeopardy rather than his vision for a second term, casting himself as a victim of “weaponization”...