In Michigan this year, a new super PAC vowing to fight pro-Israel money chipped in more than half a million dollars to help progressive Abdul El-Sayed’s Senate bid. Its funders: a crew of virtually unknown political donors, many of whom had never given to politics before last year but have since donated up to $1 million each. In New York, billionaire Alex Soros cut checks directly to progressive politicians, including Reps. Pramila Jayapal of Washington and Ilhan Omar of Minnesota. Those donations are part of the millions of dollars that Soros and his father, George, plan to give to Democratic...