I have been impressed with the actions and attitude of US Secretary of State Anthony Blinken. At 62, he is the right age for a presidential run...not that he has shown any interest. It would take a Biden withdrawal from the race to open it to new candidates and people wonder who could impress the electorate since Kamala Harris falls short in that respect.
I like Pete Buttigieg too, but don't think he has the chance that Blinken might have. Blinken has featured much more prominently in the news and, in my opinion, created a good impression. Not sure if he has any political ambitions.