Last September, a proposal to amend the US Constitution to allow tougher campaign finance and election spending restrictions went down to defeat in the Senate, on a party-line vote. Afterward, an analysis by Common Cause rounded up the latest lobbying filings to find which interest groups disclosed lobbying against this amendment. Here are some of its findings:

There are no great surprises on this list. The Koch brothers' network and the US Chamber of Commerce currently raise millions of dollars of dark money to affect elections, and their opposition to campaign finance restrictions is well-known. Other conservative interest groups, including the NRA, the National Right to Life Committee, and various religious right groups are also on the list. The ACLU's opposition to the amendment might seem odd to some, but they've long opposed many campaign finance restrictions as an infringement on speech rights.

Meanwhile, government reform groups, environmental groups, the NAACP and unions — most of which tend to have progressive sympathies — lobbied in favor of the constitutional amendment. But the broad opposition among conservative groups is the key problem for campaign finance reformers. Change is unlikely to happen as long as campaign finance reform remains such a partisan and polarized issue — which means the money will keep on pouring in.