Republicans are not thinking of protecting the country's best interests they are thinking of themselves.
A number of them are thinking this failure will push Boehner out of the head position and they want the position for themselves or their tea party brethren.
A number of them think that if the country goes over the cliff, it will result in magical smaller government.
A number of them think that if the country goes over the cliff, it will result in blame being placed on Obama and the Democrats.
They are wrong on all counts (although Boehner is probably finished).
The GOP has learned nothing from the election and nothing from Gingrich's shutting down the government fiasco.
When payroll taxes increase and when military contracts get cut, the blame will go straight to the GOP. The could have done something, but protecting the super rich from infinitesimal tax increases was more important. Once the blame settles, then the GOP will really start to howl and fling their feces just like their howler monkey instincts tell them to do.