Yes, strictly speaking. It is used to bolster the sense of unlikelihood.
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Yes it's a redundancy. Could means is potentially. Potentially is an adverb originating from potere (Latin), which is the verb ''to be able (to)''. It is extremely overused in the UK, and another example of people trying to sound cleverer than they are, and they generally use it a lot. The same type of people who use literally incorrectly, and overly so.
I also consider "could potentially" is incorrect. "Could" indicates possibility and so does "potentially" so why use them together? It is more natural to say "This could affect me" rather than "This could potentially affect me" - note the different intonation.