Technically, everyone who has a license or permit is a potential juror. (at least in florida, I'm not sure how they do it on other states.)

It's a very fine line in this situation, but his laying out the crime according to him, his past rhetoric against people who disagree with him, and past attempts at influencing public opinion, I believe this could count. It's not a violent call to action, it is an influence scheme, which is still considered jury tampering. Like I said, there is a reason they make a base public statement and let their lawyers do the talking.