First of all, it's not neck to neck.But neck and neck.
Although there is a tendency to say neck to neck in few countries, it is wrong to do so.
When you say that a particular race or contest between two participants was neck and neck, what you are implying is that it was very even or very close. Either of the two participants could have won it.
Here are few examples:
• The survey shows that the two political parties are running neck and neck.
• At the two-mile mark, Mohan and Sham were running neck and neck.
• Atilt and Vishnu were running neck and neck in the quiz competition.
Neck and neck comes from the world of horse racing.