Sen. Chuck Hagel (R-Neb.), pictured in August, 2007, will accompany Sen. Barack Obama (D-Ill.) to Iraq later this year. (Associated Press) By Jonathan Weisman Sen. Chuck Hagel (R-Neb.), an opponent of the Iraq war and a dark horse in the campaign to be Barack Obama's running mate, will accompany the presumptive Democratic nominee when he travels to Iraq soon, sources on Capitol Hill and close to the Obama campaign confirmed. Under congressional rules, an official congressional delegation trip, or CODEL, is supposed to be bipartisan. And because of logistical and security concerns, Obama's trip to Iraq would likely have to be for official Senate business, rather than his presidential campaign. So having Hagel aboard is more than a political coup -- it is a logistical necessity. Hagel spokesman Jordan Stark and Obama spokesman Dan Pfeiffer refused to confirm or deny the retiring Nebraska senator's decision. Hagel is a Vietnam combat ...