A bill that would have required political donors giving more than $10,000 to independent groups failed in the Senate July 16.
Many independent political spending groups will continue to hide their big donors now that Republicans defeated another attempt by Democrats to require such disclosures.
After the heated and expensive Republican presidential primary, many in the GOP were rethinking their opposition to the DISCLOSE Act, which would have required independent groups, including so-called super PACs, to list their major donors. But now that the general election is underway, they're singing a different tune.
The Democratic bill would have required outside groups to share the names of anyone who donates more than $10,000. Sen. Ben Cardin (D-Md.) hopes an outcry from voters will force Republicans to support the bill in the future.
"I understand that the Republicans will be united and we have little chance of passing it, but I think it's important we do everything we can to protect the integrity of our system," Cardin says. "I do think the public agrees with us."
Campaign analysts say later this year the Federal Communications Commission may require broadcasters to reveal more about the groups, some of which are making massive ad buys in places such as Virginia. Lawmakers are also expected to try to amend the Constitution to overturn the Supreme Court's 2010 Citizen United decision, which opened the door for corporations to spend limitless amounts of cash in campaigns.
In the meantime, analysts expect more negative ads during this election cycle than ever before.