When Democrats say they need a generational change in their party’s leadership, they usually aren’t referring to former President Barack Obama. Although the 63-year-old has been out of the White House for eight years, he retains his grip on the Democratic imagination. Perhaps last year loosened it some, however. Obama took it upon himself to rescue Democrats as his erstwhile vice president, former President Joe Biden, faltered. He helped nudge Biden, who was trying to hold on to the presidency at 82, out of the 2024 race. Obama took to the campaign trail for Biden’s replacement, then-Vice President Kamala Harris.  Democrats tried hard to recapture the magic of the 2008 campaign. The “joy” initially associated with Harris was billed as the successor to the “hope” represented by Obama. But it proved difficult to put the...