James Moore, coauthor of Bush's Brain: How Karl Rove Made George W. Bush Presidential, says this, flatly, in an L.A. Times op-ed piece:

The cause of the war in Iraq was not just about Saddam Hussein or weapons of mass destruction or Al Qaeda links to Iraq. Those may have been the stated causes, but every good lie should have a germ of truth. No, this was mostly a product of Rove's usual prescience. He looked around and saw that the economy was anemic and people were complaining about the president's inability to find Osama bin Laden. In another corner, the neoconservatives in the Cabinet were itching to launch ships and planes to the Mideast and take control of Iraq. Rove converged the dynamics of the times. He convinced the president to connect Hussein to Bin Laden, even if the CIA could not.

Is he overstating the case? He's followed Rove for two decades and says he's learned this from administration sources:

The same old reliable sources from his days in Texas are in Washington with him. And they say Rove is intimately involved in the Cabinet and that he sat in on all the big meetings leading up to the Iraq war and signed off on all major decisions.

In addition -- this seems very plausible to me -- Moore's sources say Rove was

present at a war strategy meeting concerning whether to attack Syria after Iraq. Rove said the timing was not right. Yet.

Read the op-ed. (If you need an ID and password, use "clipjoint" for both.)