Updated 6:17 p.m.

A stream of amicus briefs to the Supreme Court on a closely watched political spending case turned to a flood by the end the week, as Members of Congress, attorneys general and advocacy groups weighed in.

The big surprise was a bipartisan brief from Sens. John McCain (R-Ariz.) and Sheldon Whitehouse (D-R.I.) urging justices to let stand a Montana law that bans corporate political expenditures. The court is weighing whether to take up a constitutional challenge to the law, and today marked the deadline for friend of the court briefs in that decision.

“Evidence from the 2010 and 2012 electoral cycles has demonstrated that so-called independent expenditures create a strong potential for corruption and the perception thereof,” the two Senators wrote in their brief. “The news confirms daily that existing campaign finance rules purporting to provide for ‘independence’ and ‘disclosure’ in fact provide neither.”

Four House Democrats also weighed in with a brief: Reps. Robert Brady (Pa.), Charlie Gonzalez (Texas), Zoe Lofgren (Calif.) and Chris Van Hollen (Md.), who has authored the House version of a campaign finance disclosure bill. The case is Western Tradition Partnership v. Montana.