In the latest display of contention over the federal Affordable Care Act (ACA), the U.S. House of Representatives on Sept. 20, 2013 voted 230-to-189 along partisan lines to defund the 2010 health reform law.

Since passage of the ACA, factions within Congress led primarily by Republicans have attempted dozens of times to repeal the law. None of these efforts, however, have yet succeeded. The latest effort by the House is similarly expected to fail given Democratic control of the Senate and the White House.

Nevertheless, the defunding measure, which the House passed as part of a joint resolution to fund the federal government for the 2014 fiscal year, has gained considerable attention because of its timing. On Sept. 30, 2013, the current federal budget will expire. If Congress does not pass a budget by then, beginning on Oct. 1, 2013, large segments of the federal government could shut down for the first time since Congress last reached a budget impasse in the mid-1990s.

Oct. 1, 2013 is also an important date for the implementation of the ACA. On that date, the open enrollment period begins in the health insurance exchanges created by the law, where individuals can compare and shop for private health coverage options. Coverage for plans on the exchanges will begin on Jan. 1, 2014, when several other major reforms under the ACA take effect, including the “individual mandate” requirement that most Americans obtain health insurance if they do not already have it.

Despite the unlikely passage of the House budget legislation in its current form, Congress could continue to debate funding and implementation of the ACA over the next several weeks. As it deliberates a budget for the next year, Congress also must consider whether to increase the debt limit to allow the federal government to borrow money past mid-October to pay its existing financial obligations. Republicans have indicated that they may seek to delay the ACA or at least certain components of the law, such as the individual mandate, as a condition to increasing the debt limit, which, if not increased, could result in the federal government defaulting on its debts.