Here's a link to Seymour Hersh's latest piece in the New Yorker, chronicling what he and his sources see as a shift in what are still ongoing plans to have some sort of military engagement with Iran before Bush leaves office. Cheney seems to be the main instigator.
Hersh thinks the possible mission has been scaled down, from a broad bombing attack on known nuclear and military facilities, to a "surgical strike" on Revolutionary Guards facilities in Tehran and elsewhere. Administration and military spokespeople have been laying the groundwork by claiming that Iranian forces are training insurgents in Iraq, so the attacks can be spun as defensive. The Senate went along with the idea of designating the Revolutionary Guards as a terrorist organization, and even with authorizing possible action against them (Hillary, what were you thinking?).
Hersh has been hyping the possibility of an attack on Iran for a long time. Thank goodness it hasn't happened yet. Hersh thinks the administration understands it hasn't sold the idea of Iran as an imminent nuclear danger, so it's shifting to a different rationale.
I still think the military is likely to talk the administration out of it. I'd like to think there's a high-ranking general with the intestinal fortitude to resign and go public over this issue if necessary, but most high-ranking generals got there through political and bureaucratic skills more than through being known to cherish fundamental American principles.