It spells disaster for the Republican "brand" -- if those who repeatedly pledged not to raise taxes now do so in an ugly "Read My Lips" redux, why should any of us ever believe any Republican politician again? If GOP leaders want to go into the semi-permanent political wilderness, they should follow this foolhardy course: It all but guarantees the emergence of a third party that will split the GOP-conservative coalition and boost the Democrats.
What's more, it's terrible policy. With a struggling economy, everyone knows that the worst thing to do is to increase the economic burden on those most likely to create jobs. Want long-term unemployment and even less economic activity? By all means, make higher income people give more to the government so that they have less to spend on the kind of activities that create private-sector jobs.
If the GOP is smart, it will reject tax increases in every form. Instead, it will promote and pass legislation to prevent the defense cuts from happening -- and ensure that the threat of massive defense cuts becomes the responsibility of the President and Democrats. Note that Defense Secretary Leon Panetta has warned against such drastic defense cuts, so legislation ensuring that they don't occur would actually bipartisan. Forcing a House vote on such legislation would have the effect of splitting the Democratic party -- rather than allowing a "supercommittee" tax increase vote that would split Republicans.
Recall also that none of the threatened defense cuts would go into place until 2013 -- that's largely after the inauguration of a Republican president IF the GOP doesn't, once again, shoot itself in the foot by reneging on a "no taxes" pledge.