The foreign policy blob has realized that even with a large anti-war movement, they don't really need to manufacture consent. The 2003 marches against the Iraq war were some of the largest in history, and they didn't have any effect on government policy. They may ultimately have led to Obama both winning the Democratic primary and being elected president, given that he positioned himself in clear opposition to the war, which Democrats in 2004 hadn't found the fortitude to do. Once he was in office, of course, things continued as before, the campaign promises forgotten. The blob knows that an unpopular war might lead to the presidency switching parties in '28, but they also know that party switches are never allowed to affect policy.
At this point, for an anti-war movement to have any affect, it would have to be in some way direct-action based, focused on the blob's ability to wage war rather than its willingness.