Open this photo in gallery: Republican presidential candidate Nikki Haley talks to a supporter during a campaign stop in Moncks Corner, S.C. on Feb. 23, ahead of the South Carolina Republican presidential primary election.BRIAN SNYDER/Reuters Bruno Loefstedt had hoped 2024 would finally be the year that brought him back to the Republican Party. Once a loyal GOP voter, the 66-year-old retired army officer couldn’t bring himself to support Donald Trump in the past two presidential elections, repelled by his divisive political style. This time around, Mr. Loefstedt thought, the party might instead nominate a candidate more in line with his...