None of the above! I detest masculine names on girls. It just sounds like you have 2 boys. If you twisted my arm, I would vote Harlow.
Seems like Harlow is a favorite! ;)
I love it.
Harlow's my favourite of all four!
Yeah, none of them...sorry...
They are too boyish and matchy with Tucker.
Harlow sounds best with Tucker, and also, Harlow is the only name on your list that says "girl" to me. The others...it's hard to tell, which isn't necessarily a bad thing, just not my cup of tea. However, as others have pointed out, Sailor/Sawyer and Tucker is a very occupational-name sibset (and it's hard to tell if you have boys, girls, a boy and a girl...) and Campbell is a little too...soupy.
Therefore, I'm voting for Harlow (though I prefer Marlow/Marlowe...I hear "Harlot", "Hollow", "Harlem" when I say Harlow out loud...though despite those associations, Harlow does still have a pretty sound to it).
I vote Harlow. Saylor and Sawyer are out b/c they are too matchy with Tucker (and not to go on a tangent, but WHY does everyone think Sawyer is androgynous? It is completely boyish to me!) Campbell is fine if you are into the surname style, and seems to be fairly accepted as unisex, so that would be my second choice.