Insiders believe and report that President Obama's Chief of Staff will be leaving on Friday to campaign for Mayor of Chicago. How will the White House and Presidential policies be different without Rahm Emanuel? Who are the likely candidates to replace him? Yesterday, President Obama told NBC's Matt Lauer that if Emanuel wants to run for Mayor of Chicago, he'd better get going. Lynn Sweet is Washington Bureau Chief for the Chicago Tribune and a columnist for PoliticsDaily.com.