That's why it makes sense to give them multiple laws that regulate abortion and ask them to rank them instead of asking them for their ideal abortion law.
They will have to give you reasons about why they prefer one exception over another even if they would reject both exceptions in a perfect world. That usually requires them to reason in a way that's more than just reiterating talking points.
Agreed, that seems like a good approach to teasing out details of a stance. (Most real people will just ignore you in various ways, of course, but if you can make them sit still long enough it's viable)
As Multiheaded added, "Personal is Political" stuff like gender relations, etc also may belong here.