"Notable" is not precise phrasing, but it should be someone who has a realistic chance to win - either someone famous, someone who can raise a lot of money, someone who enters the race with a fair number of endorsements. Lori Droste, Rashi Kesarwani, Ezra Klein, Kim-Mai Cutler, Jesse Arreguin would all qualify. Rigel re-announcing his candidacy would resolve YES.

I'm not going to bet since this is subjective enough.