Even before October 7, Jonathan Kessler had as his screensaver the Tom Petty lyrics, “Everything changed then changed again.”“For years, I’ve recognized that we’re living in an age of liminality,” said Kessler, who left the American Israel Public Affairs Committee, or AIPAC, in 2021 to start Heart of a Nation, with an aim “to empower emerging American, Israeli, and Palestinian changemakers to improve their political cultures.” He already knew, he said, that “everything’s in transition.”Even so,