Darializa Avila Chevalier won the backing of Mayor Zohran Mamdani in her bid to unseat Representative Adriano Espaillat. Then her social media history took center stage.
After Republicans redrew her district to favor their party, Representative Debbie Wasserman Schultz decided to run in a nearby historically Black district, pitting her against some Black Democrats in the state.
Mr. Trump backed Mr. Collins over Derek Dooley, a former football coach supported by Gov. Brian Kemp, a Republican whose relationship with the president is strained.