Although I think he will make jokes against all politicians as long as they don't hit too deep, I think Leno strives to be like the entertainers of old, like Carson and Bob Hope, who could be well-liked by all, and would *never* not support their country in time of war. Even Letterman strives for that. All those who last the long term must not be too political on either side but always patriotic. It is a tough balance. It would not surprise me if Leno is doing or eventually does do stints for the USO... I think he would like for that legacy that Bob Hope has.
I write topical comedy for a living myself (for radio syndication), and I can watch his monologues and tell that he's doing exactly what I have to do: do jokes about all sides to be perceived as "fair," but the anti-Bush jokes are all based on stale "comedy templates," like "Bush is dumb," "Cheney is really in charge," etc., that nobody really believes anymore. Meanwhile, his jokes about the left, like ours, are much sharper and based on actual, up-to-the-minute quotes and events. That's because liberals roll out of bed every morning (or afternoon) and go to work on their one and only job: creating raw material for us comedy writers.