Midterm elections loomed large as the Senate derailed a campaign-finance bill this year on straight party lines.

Changing the rules of the political game is always a heavy lift on Capitol Hill, but especially in a highly volatile election season that could flip control of the Congress. Not even a controversial Supreme Court ruling earlier this term, which paved the way for unlimited corporate or union spending in ads for or against a candidate, could bring a measure of consensus to the Senate.

The proposed law would have required that chief executives appear at the end of political ads, claiming responsibility for the material. The law also would have banned foreign corporations or governments, large government contractors, and federal bailout recipients from spending money in US elections.

“It is incredible that we now have to struggle to find a supermajority – 60 senators – even just to debate a bill whose principles both parties once supported and that 9 in 10 Americans want us to pass,” said Senate majority leader Harry Reid during Tuesday afternoon’s floor debate.

The measure failed 57 to 41 – essentially falling one vote short of 60 given that Sen. Joseph Lieberman (I) of Connecticut, a supporter, was absent and Senator Reid switched his vote to no to keep the option of bringing it back at a later date.

All three New England Republicans – the key swing votes on major bills – backed off the bill.

Sen. Susan Collins (R) of Maine, a moderate, said after the vote that she had supported bipartisan campaign finance reform in 2002, but that the current bill was “a highly partisan bill designed to advantage some groups over others.”

Senate Republicans targeted the exemptions for large, powerful national groups, such as the National Rifle Association and unions from some reporting requirements.

“The NRA and Sierra Club get exemptions but the Brady Group [on Gun Violence] and the American Petroleum Institute do not. It carves out certain favored groups, and that’s just not fair. It’s also likely unconstitutional,” Senator Collins said.

On July 14, Sen. Scott Brown (R) of Massachusetts announced his opposition to the bill, charging that the Disclose Act “changes the rules in the middle of the game to provide a tactical advantage to the majority party.”

Sen. Olympia Snowe (R) of Maine, the last to announce her intentions, said today that Democrats had not done enough to build consensus, including holding hearings.

In January, the Supreme Court held in Citizens United v. Federal Election Commission that corporations and other groups can spend unlimited funds to influence elections, but encouraged the Congress to require more disclosure.

“A vote to oppose these reforms is nothing less than a vote to allow corporate and special interest takeovers of our elections,” said President Obama in a Rose Garden address Monday. “It is damaging to our democracy.”

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