Private companies are in general allowed to censor what they want. Only the US government is subject to the First Amendment, not Twitter.

However, I think a case could be made that deplatforming one candidate in preference to another would be a donation to the remaining candidates campaign, and could fall afoul of some campaign finance rules.

I think if companies that provide a platform are allowed to censor content, the rules should simply be changed.

We get a lot of problems otherwise.

Twitter should just blanket ban all candidates then. Seriously, all presidential candidates, all senators, all congressmen and women, even local mayors. Ban everyone!

I would be in favor of this, paradoxically. I'd like to think many of the popular politicians would move to the same alternative platform (maybe Parler?), and hopefully pull a bunch of Twitter users with them. Anything that chips away at censorious big-tech monopolies is a move in the right direction.

> However, I think a case could be made that deplatforming one candidate in preference to another would be a donation to the remaining candidates campaign, and could fall afoul of some campaign finance rules.

Could Twitter designate itself (or a subsidiary) as a Political Action Committee so they can deplatform (or promote) whomever they like?

the us government preventing some people form seeing its communications, to a company must host content against its terms when dealing with a politician is a big line to connect

It doesn't work in both directions though. That Trump isn't allowed to block people on a private website he (effectively) uses for official business is not equivalent to that private website being required to facilitate his official business. The first amendment prevents him from blocking because it would suppress the right of the population to address their officials, but it would also support their right to deplatform him as an exercise of Twitter's free speech.

Has there been anything unpalatable shared by or sent from @potus? (I could check, but I’ve blocked the other account for my sanity.) As I understand, most of the less palatable insults come through Trump’s personal account.

Trump has been deemed to be using his "personal" account for official business by the courts, and as such they've ruled that the constitution prevents him from blocking people on his "personal" account.

I'm not sure that effects what Twitter can do at all though.