Forty-seven years ago, Maria del Carmen Guzman-Weese stood with her mother and sister to take the oath of US citizenship. Then 17, Maria suddenly turned to her mother, and said: “I love this country but I cannot be a citizen because of you. I need to want it because of me.” Three years later, Maria finally took that oath, because it was her choice, and so she could vote for Ronald Reagan. “That time it came from my heart,” she said. Many Hispanic immigrants like Maria feel a natural affinity for the Republican party — an allegiance that often bewilders...