The Democratic National Convention in Chicago last night did not introduce any new ideas, but it solidified Kamala Harris as the party’s nominee — a new leader representing both a continuation of Biden’s legacy and a break from the man who installed her as his vice president. First, Hillary Clinton, a woman whose presidency slipped away from her, took the stage in support of Harris. Clinton kept her speech focused on women voters, evoking both her own mother and Kamala’s, saying they would have urged, “Keep going.” Harris will certainly “keep going” until Election Day in November, but many vot…