Neither Obama nor Pelosi thought Harris was the best candidate.

Entirely possible. Obama and Pelosi represent different (though overlapping) wings of the Democratic party, and Harris might not have been best for either of their factions. Even assuming there is a single "best" candidate to be the nominee, it's also not unusual for that candidate to not win the primary. Nor am I saying that it's certain that Harris would have won the nomination.

But being the sitting vice president is an enormous advantage in a primary - it's very rare for an incumbent VP to enter the race and lose the nomination. The reworked primary calendar also favored Harris compared to her 2016 run, moving South Carolina ahead of Iowa and moving California out of June and onto the March 5 Super Tuesday.

Who do you think would have beaten her? I can't think of anyone but Newsom that I would think would be a favorite over her - and not by much.