I've got a text field that can potentially have multiple values.

doc 1:
 field a:"X Y"

doc 2:
 field a:"X"

I want to be able to do :

a:X^5

And have both doc 1 and 2 get an identical score.
I've been messing around with all the field options, but I always end up with doc 2 getting double the score of doc 1.

I've tried setting multiValued="true", but get the same result.

Is there someway that I can set my search or the field definition so that it will boost just based upon the existence of the search term and not be effected by the rest of the field's contents.