Ugh, really? Why Gravel? I'd rather have him stay than Gabbard. He's basically everything I like about Gabbard with none of the creepy authoritarian loving baggage, proof that there are better options out there for you if her brand of anti-establishment pro-peace progressivism is what you want. Also he's growing a lot in support and will probably make the debates. He's my number 3 right now.
Probably due to his declining health. Don't forget he's already 88 years old and needs a cane to walk, and even in his video you can see that he can only barely move. Chances that he wouldn't last through his period are pretty high by the looks of it.
Fair enough. Honestly though, I'm sincerely beginning to think that there are essentially 3 candidates that are truly major candidates with a genuine chance to win. Biden, because he's a poll frontrunner and will have the backing of the establishment, Bernie, because he's right behind and has the biggest portion of the progressive grass roots by far and will probably be the consensus progressive pick in the end, and Kamala Harris, because if Biden flames out with a series of gaffes, Harris is the de facto inheritor of establishment support, because she's acceptable to them but also has some credibility with the progressive grassroots, and thus will be seen as the unity candidate by the establishment, whether she deserves that or not. If anyone other than those three end up winning, it will be because one of the candidates knocked one of the three I listed from that role of the centrist establishment pick, the progressive grassroots pick, or the establishment backup unity pick. Of those, Harris is the most likely to change as she could easily be uprooted by Beto and her star already looks to be waning, though the California primary will give her a last chance. Bernie could possibly lose the progressive pick, but I don't see that happening, his lead is just too strong. Biden definitely won't, because if he goes under, the centrists have no one else with the necessary star power to win, so they'd move to the back up unity candidate and then that candidate would be much more likely to win.