The benchmarks, from HR 2206, Title 1 section 1314 (b) 1.
There are two noteworthy processes included in the legislation.
One, it requires the Comptroller General to review the benchmarks in parallel with the President. That position is currently held by David M. Walker. He (and the GAO) are independent of the President, he works for Congress and there is at least the potential for an interesting comparison of his answers to the President's.
Second, is this provision in section 1314 (d) :
(d) Redeployment of U.S. Forces From Iraq- The President of the United States, in respecting the sovereign rights of the nation of Iraq, shall direct the orderly redeployment of elements of U.S. forces from Iraq, if the components of the Iraqi government, acting in strict accordance with their respective powers given by the Iraqi Constitution, reach a consensus as recited in a resolution, directing a redeployment of U.S. forces.
That seems like a straightforward requirement that we withdraw or disengage if the Iraqi parliament passes a bill asking us to. I think that is more likely then Congress passing a withdrawal bill.
Gordon Smith supported it. My thoughts on the bill haven't changed, I give credit to Wyden for opposing it.