I was raised to pronounce "potential" with a long o (ō). This makes sense where the syllables are divided. Yet, the online dictionaries I have checked say it is "puh". Can you comment?
It would be too prescriptive to say it is pronounced one way or the other. I looked into some dictionary IPA spellings and they have the shwa for that 'uh' sound. Vowels are tricky things though. It might be shwa in the dictionary, but that's not a strict guideline. You might not notice it, but even you might say is as p'uh'tential if you are talking really fast...vice versa for other users (I tend to say p-oh-tential if I'm saying it slow).
Just don't pronounce it as 'carrot' and you won't raise any eyebrows.
It is normal in the majority dialect to make the first syllable of "potential" unstressed, since the second syllable is stressed, and the first syllable has a lax vowel and is open. And generally, unstressed non-high vowels reduce to schwa. All the same, I often hear tense and unreduced "o" and "e" in such initial syllables in American English. Apparently, the vowels are tensed for clarity. The words where tense and unreduced "e" (i.e., [i:]) seems to be an option are words like "eliminate", "electricity", "deliver".