There was no question, Caleb Brock thought, that Calla Walsh would become “one of the great people in politics.”He first encountered Walsh in 2020, when both were volunteers for the reelection campaign of Massachusetts Senator Ed Markey. They were part of a movement of hyper-online young progressives who helped reinvent the septuagenarian career politician as a Gen Z icon, one meme at a time.Walsh, then a 16-year-old from Cambridge, was one of the brightest stars within the loose group known as the “Markeyverse.” Unusually self-possessed, Walsh seemed singular in her ability to win attention and channel it toward her goals.The…