Story highlights Political donors will be able to give a lot more money to political parties if a massive spending bill passes Congress this week

Provisions were tucked into the bill during closed-door negotiations

A proposal to let rich donors give more money to political parties - slipped behind closed doors into a huge government spending bill -- is the latest in a string of setbacks for restrictions on money in politics and will be a "disaster for the American people," according to good government groups.

Campaign finance reform advocate Fred Wertheimer called the provision a "great deal" for millionaires and billionaires who can buy influence through big dollar contributions and for the politicians seeking them.

The $1.1 trillion spending bill, which would fund most of the government until next September, includes provisions that will allow donors to give a lot more money to Republicans and Democrats to help fund conventions, building projects and legal proceedings like recounts.

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Rather than facing the current cap of $32,400, donors would be able to give up to $777,600 each year to funds and committees run by the parties or their campaign arms. That means individuals could give $1,555,200 per two-year election cycle and couples could give $3,110,400 in a cycle, according to several campaign finance groups who have studied the legislative language.

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"If this passes it will be the most corrupting campaign finance provisions ever enacted in the history of the country," said Wertheimer, whose non-partisan group Democracy 21 has sent a letter to members of Congress urging them to vote against the bill. "The campaign finance laws have been left in shambles first by the Supreme Court and then potentially by the Congress if this becomes law."

Watchdog groups see the move to chip away at the limits placed on donors as the latest step in a slow unraveling of the campaign finance rules put in place by landmark legislation like the McCain-Feingold bill. Known formally as the Bipartisan Campaign Reform Act of 2002, the legislation, among other things, limited how much individuals and corporations could donate to national parties. But in its April decision in McCutcheon v. FEC, the Supreme Court struck down limits on the overall campaign contributions individual donors can make to candidates, political parties and political action committees.

That decision followed the court's 2010 Citizens United ruling that the First Amendment allowed unlimited independent political expenditures by corporations, labor unions and certain nonprofit advocacy groups. Citizens United opened the floodgates to massive corporate spending in elections and these latest provisions would be a step in that direction when it comes to individual donors.

The fear is that allowing more big money in politics places more power in the hands of big donors, effectively taking it away from individual voters. David Donnelly, the president of the pro-campaign finance reform organization Every Voice, said Americans who care about everything from taxes to the high cost of college to clean air and water should care about changes to campaign finance rules, because Congress plays a role in all of those areas.

"Every single one of those decisions is impacted by money in politics," he said. "It's about who does Congress work for and Congress right now is changing the rules so that they are going to work even more than they are today for the wealthy and well connected."

Wertheimer said if the language makes it to President Obama's desk, he should veto it to avoid enabling the campaign scandals that are sure to follow. Lisa Gilbert, Director of Public Citizen's Congress Watch Division, agreed that the administration should make campaign finance reform a veto issue to send a message to the new Congress.

"This is a pretty scary foreshadowing of what's going to be on [Sen. Mitch] McConnell's list of to dos in the next Congress and certainly dismantling the campaign finance system is high on his priority list," Gilbert said.

McConnell filed a friend of the court brief in the McCutcheon case that the argued overall limit placed individual contributions "offends the First Amendment."

"Contribution limits restrict the rights of speech and association of both the contributor and the recipient of the contribution," he wrote.

Meredith McGehee, policy director at The Campaign Legal Center, a non-partisan organization that analyzes campaign finance laws, said she hopes there are enough provisions in the bill that raise the ire of enough Democrats and Republicans to stop it, otherwise it candidates will now be in the business of asking for even larger donations than they already are. While the new language would not change the limits on contributions to individual candidates, it is often the politicians themselves who solicit donations on behalf of their party committees.

"What you're now doing, if this provision goes into effect, is putting candidates out there soliciting for contributions of $1 million plus and that's the nexus for these contributors; they want the credit," said McGehee. "They are businessmen. This is a return on investment."

The House is expected to vote on the bill Thursday, but Democrats in Congress have already raised alarms about the provision, with Minority Leader Nancy Pelosi saying it "would work to drown out the voices of the American people and massively expand the role of big money in our elections." House Speaker John Boehner argued that these and other provisions were "worked out in a bipartisan, bicameral fashion or they wouldn't be in the bill."

One campaign finance reform advocate noted that if these provisions become law, mega-donors who would have maxed out on individual contributions will have to hold onto their seats in the face of a flood of new "asks" from politicians and parties.