The stumbling block is whether insurance plans that get federal money are completely barred from covering abortions, or whether they can cover it as long as they require customers to write separate checks for the procedure using their own money.
Why does that matter?
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Because the House and Senate solved the dispute in different ways, neither of which makes everyone happy, and now they have to find a further compromise.
"Something's going to have to give," said Rep. Bart Stupak, Michigan Democrat, the pro-life author of the abortion language in the House.
At this point, it's not clear what that will be, although talks to resolve the issue have already begun and all involved in the intraparty dispute say they want to be able to support a final health care bill.
"We want to see a health care bill passed, and we don't think it's particularly helpful for anyone to draw a line in the sand," said Rep. Diana DeGette, Colorado Democrat, a leader of the House Pro-Choice Caucus.
Abortion threatened to derail both the House and Senate legislation before last-minute compromises satisfied pro-life Democrats in both chambers. But those hard-won deals look very different.
The health bill passed by the House in November bars federal funding from going to any insurance plan that includes abortion coverage. That's a significant limitation because Congress' redesigned health care system would give federal subsidies to millions of lower-income people to help them buy insurance at new marketplaces called exchanges. Because the bulk of purchasers in the exchanges would be receiving federal subsidies, most, if not all, insurance plans would be receiving federal money and therefore would be barred from covering abortion.
Mr. Stupak's House language does allow insurers to offer separate rider policies covering only abortion, but pro-choice activists contend that such policies would be unlikely to materialize because there'd be little market for them. They note that most women don't plan for abortions ahead of time.
Abortions in the first trimester typically cost between $350 and $900, according to Planned Parenthood.
The Senate's abortion compromise was designed to secure support from moderate Nebraska Democrat Ben Nelson as the critical 60th vote for the bill, headed for final passage Thursday.
Mr. Nelson offered language nearly identical to Mr. Stupak's as an amendment on the Senate floor, but it was defeated 54-45.
Democratic leaders then scrambled for a compromise that would satisfy him. In the end, Mr. Nelson worked with Senate leaders, White House officials and Sen. Barbara Boxer, California Democrat - representing abortion rights supporters - to come up with a deal.
That would allow health plans that receive federal subsidies to sell insurance plans covering abortion. But those plans would have to collect separate premiums for the procedure from customers and keep the money in a separate account from federal funds. Additionally, states would be allowed to block health plans operating in the new exchanges from covering abortion.
Mr. Nelson said the language achieves his goal of ensuring that no federal money may go for abortion. Mrs. Boxer said that although it wasn't her first choice, it still allows women to obtain abortion coverage. The deal has been rejected by outside groups on both sides of the issue - something that Mrs. Boxer and Mr. Nelson both cite as evidence that they achieved a fair outcome. In a letter to senators Wednesday, leaders of the influential U.S. Conference of Catholic Bishops reiterated their opposition, contending that the Senate language "violates the long-standing federal policy against the use of federal funds for elective abortions and health plans that include such abortions."
More problematic for the final outcome of the health care bill, the Senate language has met a cool reception from Mr. Stupak, who said that he and 10 or so other House members could oppose the health care overhaul if it's included. But Mr. Stupak is showing some flexibility. In an interview, he termed the language "unacceptable," but also said he's not yet ready to say he would oppose a final bill over that issue alone.
"I do believe this is not an insurmountable issue. I think it can be worked out," said Mr. Stupak, who's talking it over with Mr. Nelson and others.
Pro-choice lawmakers in the House also are evaluating the Senate language. After being taken by surprise when talks in the House broke down and Mr. Stupak got his way, Mrs. DeGette and others in the Pro-Choice Caucus are vowing not to let it happen again and say they won't support a final bill that goes beyond existing law.
Currently, an annually renewed law called the Hyde Amendment - named for then-Rep. Henry J. Hyde, Illinois Republican, who sponsored it in the mid-'70s - bars the federal government from covering abortions under Medicaid except in cases of rape, incest or where the life of the mother is threatened. Similar prohibitions cover other federal programs, although states may choose to pay for abortion coverage for people on Medicaid if they do it with state funds.
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