Progressives are on the quiet hunt for a new generation of leaders, eagerly awaiting the outcome of the midterms to plot their next steps. “We’ve been talking about fresh blood for years,” said one Democratic strategist who reluctantly supported President Biden in the 2020 election. “Years! And every time we go back to the dinosaurs because we say we have nothing better.” Progressives’ two biggest national fixtures — Sens. Bernie Sanders (I-Vt.) and Elizabeth Warren (D-Mass.) — themselves aren’t young and some in the party are ready for a blank canvas in 2024 or beyond, particularly if Biden decides not...