one toe over the line

One toe over the line is a phrase which refers to going just a little bit too far which is frowned upon or disliked entirely. Literally, the idiom refers to a race in which one person has a toe over the line which is not allowed before the race begins. Figuratively, this phrase is referring to the fact that when you have a toe over the line by going a little bit too far in order to get ahead, it will be frowned upon and not allowed by most people.