If there was reasonable suspicion that people involved in the Trump campaign were committing federal crimes, then the FBI could reasonably "spy" on them, except they would call it investigating. It's still gathering information about a target without the target being aware.

The only thing that would be improper is if they allowed a political opponent of Trump to find out some confidential information.

There's no indication that anything from the Trump investigation was shared with Hillary, and there's no indication that Obama asked for anything more then a summary of what laws may have been broken. If Obama had asked Comey to tell him what the Trump campaign was planning to talk about at their next rally, that would be a big problem. If Obama just asked Comey things like, "do you need more time or more people to prevent future hacking or investigate hacking that already took place?" that would be fine.

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