The grueling 2011 budget debate that brought the federal government to the brink of a shutdown might end up looking mild in the face of the next fiscal battle: the debt ceiling. That's because Republicans are openly threatening to use the calamitous possibility of a U.S. default as leverage to exact major spending cuts from Democrats.

"The president says, 'I want you to send me a clean bill .' Guess what, Mr. President. Not a chance you're going to get a clean bill," said House Speaker John Boehner (R-OH), the most powerful Republican in D.C., at a fundraiser this weekend. "There will not be an increase in the debt limit without something really, really big attached to it."

If it wasn't clear what Boehner was referring to, House Majority Leader Eric Cantor (R-VA) said it plainly on Fox News Sunday: "[T]here is no way that we Republicans are going to support increasing the debt limit without guaranteed steps being put in place to ensure that the spending doesn't get out of control again."

Calling it a "leverage moment," Cantor said Republicans will demand "spending caps, entitlement reform, budget process reforms -- these are the kind of things that we're going to have to have in order to go along with the debt limit increase."

Other Republicans have likewise rebuffed White House requests for an up-or-down vote on the debt limit.

Treasury Secretary Tim Geithner warned last Monday that the U.S. would likely reach its $14.3 trillion debt ceiling by May 16, and have "no headroom" to borrow by July 8 even under extraordinary measures if Congress fails to increase the limit.

Geithner said that failure to act in time could incite "a financial crisis potentially more severe than the crisis from which we are only starting to recover."