Confused about when the subjunctive is triggered

Question

In the quiz question: "¿Crees que ellos me ________ ese favor?

Do you think they would do me that favour?" We're told to put hacer in the conditional. If the sentence had instead started "¿No crees que..." what would the correct tense be for hacer?

Accepted Answer

Hola R
If you ask in a negative way: ¿No crees que...? it would still have the conditional:
¿No crees que ellos me harían ese favor?
but it would also admit the subjunctive, for example:
¿No crees que ellos me hagan ese favor?
This last one using the present subjunctive would lose a bit the nuance of "them wanting to do the favour" that the conditional has. The first one is saying something like:
Don't you think they would do me that favour? ( =would be willing to do it?)
While the subjunctive would be more straight forward meaning simply:
Don't you think they will do me that favour? 
I hope this is not confusing, it is a tiny nuance.
Saludos
Inma

Answer

Thanks. In this case I see the distinction. Of course, I'm not sure I will ever get sufficiently fluent that it will matter.