Since the Republicans are right on the War on Radical Islam, and since that is the defining issue of our time, and since, for the moment, most Americans agree, there is a strong temptation to try to ride this issue to victory after victory.
This would be a mistake with potentially tragic consequences for the party, and worse, for the country.
At the most basic level, the war is only one issue, and one that operates primarily (although not exclusively) at a national level. Focusing on the war makes it easier for down-ticket large-government Republicans to recreate the successes of Illinois and Pensylvania. Simultaneously, failing to make electoral tests of free-market economics and conservative social policy puts off serious reduction of government indefinitely - since those issues never win a mandate.
More importantly, though, acquiescing in making the war a partisan issue makes it almost impossible to win the war. Bruce Catton, in a series of lectures, published as America Goes to War, points out that the Civil War - and any war in a democracy, really - is as much a political problem as a military one.
Lincoln understood that the war couldn't be won if it became a Republican War. Lincoln was able to co-opt prominent state and local Democrats through the device of the "political general." Whatever their military shortcomings - and it's far from clear that they, rather than the professionals - did the lasting damage to the war effort - political generals served to keep the war non-partisan, and to keep the country generally unified on the issue.
In allowing the War on Radical Islam to become partisan, and by not co-opting lower-tier Democrats, every election becomes a referendum on the war, even if that's not the issue forwardmost in voters' minds. In means that in order to win the war, Republicans have to win every time, and in a 48-48 (or even 52-48) country, that's just not going to happen.
Now it's no good saying, "the Democrats wouldn't allow that this time - they were too set in their Bush-hatred." Even given that certain elements of their party were beyond hope, it's the President's job to find a way to get as many of them on board as possible. The longer we wait, the more powerful the anti-war voices get within the Democratic party, and the harder the job gets.