NRO's Byron York sees the Romney win in Michigan as heralding " a new, decidedly post-war-on-terror feel" for the GOP race. He sees this as a bad thing insofar as Republicans might start making non-conservative promises to ease voter pain, something York's colleague Rich Lowry is already concerned about in Romney's case.
Looking ahead to the general, the default assumption would be that a 1992-like "glum mood" is politically great for Democrats, who usually win when the economy dips. But, then, Ronald Reagan was elected in 1980 after a period of economic malaise, in part on the argument that America had grown weak in the face of nasty Middle Eastern nations who were warping our economy with inflated oil prices. To be sure, Reagan ran against a Democratic incumbent whereas the '08 race will likely be in part a referendum on the Bush GOP years. But it's easy to imagine a Republican nominee treating the stalled economy as matter of security and national strength in the hopes of blunting the Democrats' inherent advantage in that realm.
P.S. This item had me reading some old clips on the '80 campaign, including this NYT story in which Carter is quoted assuring Americans that "we've reversed decades of dangerous and growing dependence on foreign oil" and that he has a program "to secure America's energy future." Some things never change.