We don't know exactly what the campaign did yet for sure, but it is believable that the campaign tracked journalists. Until further evidence is given there is no reason to believe that these reports are false. Hopefully we will know one way or the other soon, and we will be given concrete evidence.
Hacked e-mails showing the Clinton campaign secretly tracked journalists, might be credible. The US presidential elections is one of the biggest events in America and campaigning for these elections is a huge job. Campaigners have just one agenda in mind, that is to win, hence it is no surprise that reports of Clinton campaign secretly tracking journalists might not be false. However, it also raises questions about the privacy and security of email accounts.
Yes, the report that the Clinton campaign secretly tracked journalists is credible. Journalists are a vital and very powerful part of elections. Candidates depend on journalists and news media. It is likely all campaigns track journalists secretly or otherwise. The question is whether any laws were broken in the process.
The emails that this report talks about was received through unethical means, so there should be some skepticism as to its validity. This does not mean that the tactic of tracking individuals in an effort to maintain some level of control is totally inconceivable. However, I am sure that many politicians and other public figures use this same strategy. It sounds like something a public relations professional would do. This is just an attempt to manipulate the public's opinion about this particular candidate.