The more Republicans that defect from the compromise, the more the compromise proposal should favor Democrats, because Democratic votes become increasingly necessary to pass the thing. As much of the GOP cuts itself out of the bargain, the equilibrium point moves left.
But that's not what actually ended up happening. Instead, the more Republicans that defected from the compromise, the more the compromise proposal moved right, as the White House and Democratic leadership ineptly tried to win back those lost votes. The votes never will come back, though -- for all the chasing the Democrats have done, a good 80-100 Republicans will probably never vote to raise the debt ceiling. And in giving chase, the Democrats only gave Republicans more incentive to never compromise, because the GOP knows it doesn't risk turning the issue over to its own moderates and the Democratic caucus.
All this is fairly obvious to anyone who understands that a negotiated outcome is a function of the preferences of the participants in the negotiation. But Washington speaks its own language, in which irrelevant things like "bipartisan cover" and "taking a case to the voters" and "owning the issue" are ascribed almost mystical importance. Meanwhile, the simple logic of offer and counteroffer is laughed off and forgotten. I'm firmly of the opinion that all the best thinking about politics comes from people who remain -- mentally, if not physically -- outside the beltway; the political circuit's cognitive quirks can corrupt anyone's ability to understand Congress as anything more than a hypertrophied debate club.