I think there is a (little) difference. I think there is a "mandatory force from facts" (I am translating from Spanish "fuerza normativa de los hechos"). By example, even if I am convinced it is wiser to drive by the right side if I am in England I would think a little bit before imposing it.
If the case is so severe and clear (to me) as it is in abortion topic I would remove supports.
---------------------------------------------
Regarding the initial topic there are many politicians in Spain who are nominally RC (from left to right, including communists) whose position spread from I-don't-speak-about-this to something-has-to-be-done-but-I-do-nothing.
I think for them it is more a matter of ambition for power than obedience or not to the church. I think many of them are convinced about abortion (not because official church says so, but because of personal feelings), but they prefer not to move in order not to be moved. Other many RC politicians simply don't think a shit about ethics and so they simply do the more politically correct deeds.
---------------------------------------
I think RC Church mistake has been to stress the same tiny sexual sins as abortions. So simple people think:
1) I can't obey RC view of use of condom.
2) Priest attack even more condoms than abortion.
3) So I don't feel I have no obligation of sharing RC point of view about abortion.
I think even if you are a member of a church (or the communist party, which is more or less the same
) your organisation has the right/duty to impose you some commandments: "If you are a RC/communist/member of the society... you must drive by the right side/pay taxes...". The difference with fanatism is that these imposed beliefs can not shock with your personal reason.
I.e. "boxers" in 1900 China believed that certain movements before the battle made them inmune to bullets. Well, if the first 200 died because of bullets a non-fanatical boxer should think something.
Positive example: It is hard to me to believe in Maria's virginity but, well, since we assume it is a "special" case I have no objection accepting it. (Of course I don't believe in my female friends' virginity, even if the Pope says it)
.
Abortion is even simpler: As I said in other thread, I need no God, no Pope, no obedience to agree abortion is a crime. So RC Church ought to stress how bad was it in comparison with, say, sleeping too much. Instead of that it preferred to fight condom's battle, which was definitely lost, since you would need all your obedience to stay virgin and no-condomed to achieve a less-than-nothing purity (desirable, but that's all).