This ruling comes in the middle of a hotly contested presidential race, and it is bound to be debated fiercely between now and November. But its electoral implications are unclear. Health care reform is the signature accomplishment of President Obama's first term, and this ruling validates its constitutionality. However, despite the popularity of many individual elements of the act — prescription drug discounts for seniors, the opportunity to keep a child covered under a parent's policy until age 26, and the rollback of lifetime limits on health care benefits, to name a few — it remains unpopular as a whole, a point the president himself made in his low-key, "let's move forward" reaction to today's decision. Mr. Obama's victory in court has already stirred promises from many Republican leaders to fight hard for the law's repeal, including from Mr. Obama's Republican opponent, Mitt Romney. In his own reaction to the decision, Mr. Romney promised, if elected, to make repeal of the Affordable Care Act his "Day One" priority and said he sided fully with the court's dissenters, Associate Justices Anthony M. Kennedy, Antonin Scalia, Clarence Thomas andSamuel A. Alito. But the degree to which Mr. Romney can make this issue a key to his electoral strategy is limited by his role in enacting a virtually identical act on the state level when he was governor of Massachusetts.