Senate Minority Leader Mitch McConnell (Ky.) and 35 other Senate Republicans today weighed in on the latest fight over President Barack Obama’s two-year-old health care reform law, filing a friend of the court brief urging the Supreme Court find it unconstitutional.

In March, the court is expected to hear three days of oral arguments in a case challenging the constitutionality of the law’s mandate that all Americans buy health insurance.

The Republicans’ brief argues that the entire law — formally known as the Patient Protection and Affordable Care Act — must fall if the court rules that the individual mandate is unconstitutional.

“In addition to determining the constitutionality of the mandate, that individuals purchase health insurance, the Supreme Court also will consider whether the mandate is severable from other provisions of the PPACA; in other words, whether the other provisions of the law are legally viable in the event the Court finds the mandate unconstitutional,” McConnell said in a release. “We believe the mandate is not severable from the PPACA because the law will not function as its Congressional proponents intended or achieve their objectives without the presence of the mandate.”

Republicans have weighed in previously against the PPACA in lower courts since the law’s enactment in 2010.

“Senate Republicans have twice submitted an amicus brief in the lower courts in support of the states and private parties that are challenging the PPACA in federal court,” McConnell continued. “This would be the first of two amicus briefs filed by Senate Republicans in the Supreme Court case.”

The other GOP brief is expected to make the case against the constitutionality of the individual mandate.

McConnell’s brief comes as 117 House Republicans, including Minority Leader Eric Cantor (Va.), joined the American Center for Law and Justice in an amicus brief making the same case: that the individual mandate cannot be severed from the health care law and that the entire law is unconstitutional.

Both briefs contend that the mandate is critical to the law and it cannot operate without the mandate.

“Without the individual mandate, the [law’s] remaining provisions cannot function properly,” the ACLJ brief said. “Thus, the unconstitutional individual mandate is not severable from the [law], and the entire Act must be invalidated.”

American Action Forum also filed a so-called severability brief today, which included more than 100 economists.

The White House also submitted an amicus brief today arguing that Congress has the right under the commerce clause of the Constitution to require a minimum level of health insurance coverage.

“As Congress found, the uninsured consumed approximately $116 billion in health care services in 2008 and providers were not compensated for $43 billion of that total,” the brief said. “Those costs are shifted to other market participants, raising the average family’s annual health insurance premiums by more than $1,000.”

“The minimum coverage provision plays a critical role … by regulating how health care consumption is financed,” the brief said. “It creates an incentive for individuals to finance their participation in the health care market by means of insurance, the customary way of paying for health care in this country, and it works in tandem with the Act’s other provisions to expand the availability and affordability of health insurance coverage.”