Laura Loomer, a Jewish right-wing activist known for her anti-Muslim rhetoric, has won the Republican primary in the southern Florida congressional district where President Donald Trump votes. The primary win caps a rapid rise for the 27-year-old political activist, whose provocations — and the responses to them — have made her a favorite of the right wing of the Republican Party. In 2017, Loomer, who calls herself an “investigative journalist,” was banned from Uber for calling on the rideshare service to allow riders to reject Muslim drivers. In 2018, Twitter suspended her account after she called Rep. Ilhan Omar, then...