This sounds like an incredibly poorly designed "study". They compared neutral answers from ChatGPT to answers given when instructed to pretend to be a political

This sounds like an incredibly poorly designed "study". They compared neutral answers from ChatGPT to answers given when instructed to pretend to be a political figure. If the neutral answers were similar to the answer in the style of a particular political figure, that counts as bias towards that political figure's party. Which is utterly ridiculous on so many levels. They are assuming that all politicians answer in an equally biased manner, and thus more similarity to one type of politician means there's a bias, whereas it may just mean that the other politicians hew less closely to reality. Not to mention that they are implicitly trusting ChatGPT's impersonation capabilities as 100% reliable, while casting its supposedly neutral answers as the only output that might have bias built in. Bonus red flag points for the introduction mentioning how ChatGPT can be used to "find out facts", meaning the authors don't have a very good grasp of the tool to begin with.