And if he wins the presidency, he's going to try to use his power to make those fits matter. I seriously don't see how people look at this man and think he's a good option.
It all gets publicity, and he won in 2016 on the back of months of free outrage publicity. All the time our attention is on him, it's not on his opponent.
What is even the grounds for this? You can't call election interference on a private company because of a preference for a candidate. That's like if Harris wanted to sue Fox News for a bias towards Trump. Private companies are allowed to have biases.
It is also completely possible that the supposed preferential treatment may be due to public opinion and news reporting. Kinda like how if you lie a lot, people call you out on it, but that doesn't make it illegal that they don't call out your opponent equally as much.
For a company that is a monopoly - you should logically be able to, monopolies are not allowed to have biases (shouldn't exist in the first place though).
For a company that says it's a search engine but in fact meddles with recommendations - you should logically be able to, they are calling themselves not what they are in fact.
Both would mean putting all the big tech top management into jail, though. So no chance.