In this case, from the always-interesting economics blogger Megan McArdle :
The original compromise, segregating the funds so that the federal subsidy wouldn’t pay for the abortion part, was a transparently ineffective gimmick.How transparently ineffective? If it really was just her money buying the coverage, the rider/segregated funds distinction wouldn’t matter. Obviously, the reason it does matter is that funds from some other party—possibly a pro-life party—would be helping to pay for the abortions, either through the fungibility of tax transfers, or premium pooling.
I don’t see how anyone ever thought this was going to fly; there are (as we just saw) more pro-life members of the House than pro-choice, and they’re not actually total idiots.