Surely, it is whether you are capable of arguing both sides. It is not something that we do in ordinary life, but I did a lot of debating at university - a situation where the only thing that matters ia winning the debate - and I could persuasively argue either side of almost any debate - and did.
What you never do is pretend to believe the side you are arguing on. For the duration of the debate you must rally believe in the cause you are voting for. I mean it is only just an hour. It is what actors do all the time.
If you feel strongly about something and wish to win someone over to your way of thinking, you need first thoroughly know their mindset and fully understand all the arguments in favour of their side, because only then can you use their arguments to convince them you are right, or that there is some merit in the opposite view point.
This is why people of any political party, who spend their time abusing their opponents, while at the same time trying to win them over to vote their cause are so misguided, apart from the fact that people who you abuse usually end up with an implacable dislike of you, but if you are to get them think differently you need first to understand why they vote as they do, and then use that to win them over. There is no better way of doing that than letting them see you understand their views and where they are coming from.
Think about that famous interrogation technique known as good guy/bad guy. After a doseof nastiness, the good guy will come in, sympathise with the suspect, understand their point of view and then quietly turn it round so that the suspect tells things because he thinks the good guy is on his side.