Pelosi & Co. thus aborted a bipartisan effort to ensure that if we do go to war again, we do it the constitutional way, and we do it together.

...Nothing in the provision would have prevented Bush, as commander in chief, from responding to an Iranian attack or engaging in hot pursuit of an enemy found in Iraq. Nor would the provision have prevented Bush from threatening Iran. It would simply have required him to come to Congress -- before launching all-out war.

Now Pelosi has, in effect, ceded Bush carte blanche to take out Iran's nuclear facilities. It's all up to him and Cheney.
...

commentary from Patrick J. Buchanan.