Split something down the middle - Idioms by The Free Dictionary
split something down the middle
split (something) down the middle
To divide or share the cost of something exactly equally. While I appreciate the offer and the sentiment, I insist that we split the bill down the middle—I don't like someone paying for me on a first date.
split something down the ˈmiddle divide people into two groups, who disagree: The local Conservative party is split down the middle on the matter of taxation.