If that is the attitude of the Republican nominee, mark my words, he will lose in the general election. Republicans cannot afford to be divided next year in November. If we cannot pull together by then, we will deserve the Democrat President we help to put into office.
I think Republicans WILL pull together. They'll pull together in looking forward, not backwards, and in forging a new course. It's really a blessing that the Bush admin has no successor, or else we'd REALLY be looking at a DEM president. As it is, we get a clean slate, which is a good thing. I don't think the nominee has to run away from policies, per se, but they will most likely want to be seen as a fresh start, not a continuation. Some policies started under Bush will remain, but with a new face, as it should be.