I do wonder if the US had a nationwide referendum, which question lead to a result closest to current partisanship and be the most divisive?
Gun control could end up as a 50-50 issue and match partisanship, but I'm not sure if it is the most divisive issue. Anything racial would be incredibly divisive but it would be hard to get a question that doesn't favor one side. After all, many moderate Democratic positions on it poll well but a question that leans too much to the 'abolish ICE' or 'defund the police' side would likely be a blowout the other way.
Well it depends on how gun control is phrased. Something like 'eliminate the 2nd amendment' probably fails by at least 65-35, while something like 'institute background checks for gun sales' probably passes by double digits.