Harris, 59, always had the potential to get in his way. She and Newsom, 56, rose through San Francisco and California politics at the same time. He was the city’s mayor, then the state’s governor. She was the city’s top prosecutor and then California attorney general and U.S. senator.

After Kamala Harris secured the Democratic presidential nomination in an unprecedented party upheaval, she got some advice from former President Barack Obama: Tap the campaign talent pool that is out there;