The disagreements are rooted in a letter issued by the Centers for Medicare and Medicaid Services (CMS) in August 2007. Congress was due to reauthorize the children’s health insurance program that fall, and the letter applied two principles to state programs: It targeted resources first toward families making less than 200% of the federal poverty level (now $48,500 for a family of four). If states wished to expand children’s health insurance to families with incomes greater than 250% of the federal poverty level, they had to first cover at least 95% of children in the lowest income group. The letter also instructed states to take steps to ensure that children and families were not dropping private, employer-provided coverage to enroll in taxpayer-funded programs.

Democrats reacted to the letter by refusing to vote on President George W. Bush’s nominee for CMS administrator in the Senate. The Democratic-controlled Congress passed legislation expanding children’s health insurance October 2007 and January 2008, but President Bush, viewing the bills as inconsistent with the policy goals his administration had outlined, vetoed the measures. House Republicans sustained his veto on both occasions.

Upon taking office, President Barack Obama ordered his secretary of health and human services, Kathleen Sebelius, to rescind the August 2007 memo. In February 2009 congressional Democrats enacted the children’s health insurance program expansion that had previously eluded them. Many Republicans believe the program should be targeted toward the lowest-income families, as it was initially designed. Draft reauthorization language issued by the House Energy and Commerce Committee last month would focus “funding on low-income families” to “address concerns about crowding out private coverage and subsidizing upper-middle-class families,” according to a summary.

The bipartisan deal to amend Medicare’s “doc fix” includes a two-year reauthorization of the children’s health insurance program, but policy details of that extension haven’t been released. Unless Republicans and Democrats can agree on a compromise—which eluded Congress and the Bush administration in 2007-08—one party may have to renege on policies it has adhered to for years. There are questions about the fiscal sustainability of the “doc fix,” but the philosophical questions may be no less difficult.

This post was originally published at the Wall Street Journal Think Tank blog.