• Kamala would be the most "don't change direction so shortly before the election". And I think that's the main thing going for her tbh.
• Newsom is the most charismatic and presidential. Maybe Democrats want to save that for 2028 to build up some more branding and media attention. Maybe it's already a card that has to be played now
• Michelle Obama isn't happening. Hillary Clinton didn't work, if democrats ever try the Obama nostalgia card - it can't happen with the optics of bringing someone back out of retirement in a moment of panic. Bad optics, won't happen.
• Buttigieg is like the smartest of the bunch. The guy speaks like a dozen languages or so. But he has zero presidential charisma. And also too leftist to unite centrist and liberals and normies. And he has still decades of career ahead. Save it optionally if Republicans ever nominate a moderate again

Conclusion: It's going to be probably Kamala maybe Newsom