I contend that at this point, the Bush administration is itself a serious risk to the security and safety of America.
If some new threat were to legitimately necessitate war, the Bush administration would be unable to convince Congress, the American people, and the world of its necessity.
Meaning, credible intelligence from multiple independent sources could surface demonstrating Iran was months away from nuking Israel, and Bush would be unable to muster support to stop it.
This isn't just a question of 60% disapproval ratings, or low trustworthy numbers - it's that his administration specifically lied about Iraq, and led the nation to war under false premises. Clinton lied about marital infidelity, but when he found evidence of a chance to get OBL, most people believed him. When he deployed US air-forces to the No-fly zone, we could believe him that it was necessary. Yes, the Hannity-crowd of Liberal-Haters didn't believe him and attacked him throughout his presidency, but the sane population could still give him the benefit of the doubt.
Hell, if Nixon had needed to go to war after Watergate but pre-resignation, he would have been more believable.
With Bush, other than his hard-core supporters, no one believes him anymore.
He cried wolf. Let's hope and pray a real wolf doesn't surface before January 2009.