Democrats and Abortion

To re-open a debate that most of you have probably had enough of,  this piece from the Chicago Tribune seems relevant to our discussion of the connection between abortion and legality.  According to the Tribune:

Reaching out to more moderate, churchgoing voters with misgivings about abortion, House Democrats plan to unveil legislation on Thursday that sets a public policy goal of reducing abortions in America.

The proposal, to be announced at a news conference attended by the House Democrats' national campaign chairman, Rep. Rahm Emanuel of Illinois, would not restrict access to abortion. Instead, it promotes such preventive measures as funding for contraceptives and expanded sex education geared toward avoiding pregnancy as well as support for adoption and services to new mothers, according to several people familiar with the legislation.

First off, this seems perfectly consistent with the Democratic Platform, which says that abortion should be safe, legal and rare.  It also seems consistent with a view that abortion is evil and something that we should work to eliminate, whether through legal prohibition or changing people's minds/actions, although I'm sure most of the people putting this proposal forward would not put it quite that way.  But it raises some interesting questions.  Let's assume for the sake of argument that the actual numbers of abortions under a system of legal prohibition would not drop significantly but would simply move underground (with predictable consequences for increases in deaths by women due to botched abortions).  Let's also assume that these proposals by the Democrats would cause a substantial drop in the actual number of abortions.  Setting aside questions concerning the morality of contraception (about which there's substantial disagreement on this site), would that be a reason to favor the Democratic position on abortion over the Republican position? 
And, if you favor the Republican position, is it because you think the assumptions are implausible or is it for some other reason?  If the former, then the preference for the Republican position seems to rest on some pretty unproven empirical assumptions.  If the latter, what is the basis for the assertion that abortion must be illegal (and not just, say, rare)? 

My sense of the magisterium's teaching on this is that it is closer to the view that abortion must be illegal, irrespective of the consequences of that prohibition (i.e., even if its prohbition does nothing to make it more rare).  And, given the clarity of the magisterium's teachings on this matter, a Catholic who favors the legal status quo but advocates strong policies that might well lead to a significant drop in the actual number of abortions (i.e., a Catholic who in good faith believes in the truth of my two assumptions) is pretty squarely outside the boundaries of permissible dissent.  I have to say, though, that I have a hard time squaring that conclusion with Aquinas's and Murray's discussions of the complex relationship between moral and legal questions. (HT Daily Kos)