He immediately alienated a significant portion of the electorate, which despises Code Pink.
Voters had a chance to send a message to Code Pink in 2006, 2008 and 2012. They could support the GOP in 2006, which backed Bush 100%, or Hillary in the 2008 primaries, who voted for the Iraq war, or McCain in the general election, who was the war's strongest booster in the Senate and wanted another one with Iran. Or for Santorum in the 2012 primaries. Or even for Romney, who was more pro-war than Obama.
What was the message?
By the way, this is entirely a political question. What's more popular post-2006? Supporting the Bush policy in Iraq or opposing it? I believe Obama's victory over Hillary was at least half due to his opposition to the war in Iraq. I know that as the GOP has spent less time defending the war and focusing on bread and butter issues like taxes, spending, health care reform and principles like consitutional rights they've gained ground.
Why do you think defending Bush's policies or even resuming them would be a winning issue in 2016?