If only Bush and his cohorts had the talent to "Talk Up" the administration's real success, we wouldn't be in this mess. Which is not to say that Newt is doing the right thing.
Talking Bush down only adds fuel to a fire that is only going to warm Democrats. Yeah GW is in zombie-land at the moment, but Newt is certainly not forced to point this out. And after all, what 8-year president didn't go on a long slide in his remaining "lame-duckness?"
If nothing else, it alienates all the people of principle who think you shouldn't violate Reagan's 11th commandment. But I have a bigger concern about Newt, and that is his propensity to "teach" and to therefore blab in such a way that he opens himself to major gaffes (such as the "whither on the vine" line over Medicare). Look at Reagan. He "taught" in very simple concepts and phrases. But Newt has a tendency to try to explain all the details, and on a campaign trail, that's a disaster.