In 2000, George P. Bush — then 24 and about to enter the University of Texas Law School — recorded a Spanish-language ad for his uncle’s presidential campaign. He looked primed to be his storied family’s next standard-bearer, updated for the 21st century: bilingual, telegenic, the son of a governor and an immigrant from Mexico. The campaign’s ad maker, Mark McKinnon, took to calling him “47,” in anticipation that “P,” as he’s known to friends and family, would before long join his grandfather (George H.W. Bush, 41) and uncle (George W. Bush, 43) in the American presidential pantheon.