Until about 18 hours ago, it had been Republican orthodoxy on Capitol Hill to oppose any raising of the debt limit that did not also include provisions for spending restraint or some other form of fiscal discipline. The whole point of the 2011 debt limit negotiations -- the talks that led to sequestration spending cuts -- was to strengthen the precedent for requiring spending controls as part of any debt limit agreement.

But now, House Speaker John Boehner has signed on to a proposal that would raise the debt ceiling, at least in the short term, without any corresponding cuts. House Republicans have embraced the proposal for their own reasons, but there are signs that reaction among Senate Republicans will be very, very negative.

"This is an idea that nobody would have associated with Republicans yesterday," says a Senate GOP aide. "There isn't a Republican in Congress who supported the idea of a clean debt limit increase without strings attached before yesterday." Perhaps that's an exaggeration -- maybe there were very few who would have supported such an idea -- but the aide's observations are generally accurate. They're certainly true of some of the most influential Republicans in the Senate.

The aide pointed to the relatively small group of House lawmakers and outside groups who are most committed to targeting Obamacare, even at the price of a partial government shutdown. "It's pretty obvious they are so invested in the shutdown strategy that they are willing to have an overnight conversion to the view that clean debt limit increases are somehow good policy," the aide says. "That is heresy for a conservative, and yet they are swallowing it because they are so invested in this shutdown strategy working."

One development that has been particularly surprising to some Republicans has been the position taken by Heritage Action, the political arm of the venerable Heritage Foundation. On Wednesday, Heritage Action chief executive Michael Needham signaled that his group would accept a clean debt limit increase if it would keep the Obamacare-shutdown strategy going. Today, Needham released a statement saying Heritage Action would not hold a vote for a clean debt limit increase against any lawmaker.

"We do not support clean debt ceiling increases," Needham said, "but because Heritage Action is committed to giving House leadership the flexibility they need to refocus the debate on Obamacare we will not key vote against the reported proposal."

The end result is a brand-new split among conservatives and Republicans over the question of raising the debt limit. Before the last few days, there was no such split. Now Republicans, especially those in the Senate who are not part of the new agreement, will have to explain why some of their number are in favor of raising the limit while receiving no spending cuts of fiscal concessions in return.