The Supreme Court’s decision to uphold the Affordable Care Act has, over the past several days, brought attention to congressional races that have been largely overshadowed by the presidential election, with Democrats and Republicans differing Sunday about the impact of the ruling.

Which party holds the majority in either or both the House and Senate would be a major factor in Capitol Hill efforts to repeal the health care legislation signed into law by President Obama in 2010.

Senate Minority Leader Mitch McConnell told “Fox News Sunday” the races in his chamber will be “a referendum on this job-killing, health care, tax-increasing measure.”

McConnell, R-Ky., also suggested incumbent Senate Democrats seeking re-election in November will face a difficult challenge because all of them voted in favor of a law “deeply unpopular with the American people.”

McConnell also said, “We have one last chance here to defeat ObamaCare. We can do that in the November election.”

The chamber is now controlled by Democrats 53-47. Thirty-three of the 100 seats are being contested in the November election -- 10 Republican, 23 Democrat and two independent, which typically caucus with Democrats.

All 435 seats are being contested in the House, which is now controlled by Republicans 242 to 191.

Maryland Gov. Martin O’Malley, speaking on CBS’ “Face the Nation” said fellow Democrats should campaign on the merits of the legislation, despite many losing their seat in 2010 because of Tea Party supporters unhappy with their support for the act.

O'Malley said his party “needs to do a better job” of saying the economy will never improve if the federal government continues to throw away money on expensive health care “for fewer people with worse and worse outcomes.”