A small but vocal group of Republicans, including some freshmen, in both chambers are rebelling against their party leaders as they form what they hope is an impenetrable firewall against a debt-limit deal that would exclude significant spending cuts and a balanced budget constitutional amendment.

The “Cut, Cap, Balance” pledge has been signed by just 12 senators and 28 House members. Their mission is to oppose any move to raise the borrowing limit unless it’s accompanied by significant spending cuts and caps, and to pass a balanced-budget amendment to the Constitution.

But by setting a high bar for a debt-limit vote, the conservative rabble-rousers virtually ensure that House Republicans, who hold 240 seats in the lower chamber, will need the support of some Democrats to reach the 218-vote threshold for passage of a debt-limit increase. And that’s a tall order as some Democrats are already pledging to block any deal that cuts key priorities.

Among the congressional signers of the pledge are the newest Republican members of the House and Senate. Six of the 12 Senate Republicans signers are freshmen, as are 17 of the 28 House Republican signers.

Others pledge supporters are more seasoned conservatives, such as Republican Study Committee Chairman Jim Jordan (Ohio) and Sens. Jim DeMint (R-S.C.) and Tom Coburn (R-Okla.). One member of GOP leadership, freshman liasion Rep. Tim Scott (R-S.C.), in either chamber has thus far signed the pledge.

On Thursday afternoon, after bipartisan congressional leaders met with President Obama and Vice President Biden at the White House, some pledge supporters held a news conference on Capitol Hill renewing their call for significant reforms to be included in a debt-limit deal.

The group of senators, which was led by Senate Tea Party Caucus founders Mike Lee (R-Utah) and Rand Paul (R-Ky.), also included some Republicans who had not signed the pledge. The senators announced that they are introducing standalone legislation to “cut, cap and balance” the budget.

“The one way we can bind a future Congress, one that’s not in power now, is through a constitutional amendment,” Lee said at Thursday’s news conference. “We’re identifying here today that this is one way that we could raise the debt limit. ”

Interest in such a pledge extends beyond the Senate to the House, where the group of conservatives who have thus far signed on to the “cut, cap, balance” pledge is smaller than the coalition of members who in February successfully pushed House Republican leaders to redraft their fiscal 2011 funding resolution to include tens of billions of dollars more in cuts than leadership had originally proposed.

And in some ways, the conservative group’s clout is more limited than than their clout n in the government-shutdown debate. By making their support for a debt-limit extension dependent in part on the passage of a balanced-budget amendment instead of on a specific cut amount, the pledge signers have essentially ceded their leverage to Democrats – a point House Majority Leader Eric Cantor (R-Va.) touched on Wednesday when he told reporters he would not be signing the pledge.

Sen. John McCain (R-Ariz.) also came out Wednesday against any move to tie the debt-limit vote to passage of a balanced-budget amendment.

The pledge signers simply can’t pressure House Speaker John Boehner (R-Ohio) and other Republican leaders to force Democrats to vote for a balanced budget amendment in the same way as they were able to persuade their own leaders to increase the size of a spending cut to stave off a government shutdown.

The several dozen Republicans signing the pledge have also succeeded in helping to bring the balanced-budget amendment to the fore of the congressional debate for the first time in years. The House will vote this month on a balanced-budget amendment measure, Cantor announced two weeks ago, and the Senate may hold a similar vote in the weeks ahead.

But when it comes to the debt-limit debate, perhaps the greatest impact of the pledge has been that it ensures that Republicans will need Democratic support to raise the borrowing limit.

That move could have the unintended consequence of weakening Boehner’s hand in the ongoing negotiations.

Read more on the debt debate on PostPolitics

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