Chicago Mayor Rahm Emanuel shakes hands at a campaign office Tuesday, as voters gave him a second term. He won a runoff election against Cook County Commissioner Jesus "Chuy" Garcia. M. Spencer Green/AP hide caption

itoggle caption M. Spencer Green/AP

Chicago Mayor Rahm Emanuel failed to capture a majority of the vote last month, forcing him into a runoff. It's highlighting a divide among Democrats playing out nationally. Charles Rex Arbogast/AP hide caption

itoggle caption Charles Rex Arbogast/AP

Chicago Mayor Rahm Emanuel (center and 8th Ward Alderwoman Michelle Harris join phone bank workers Tuesday on Election Day in Chicago. Emanuel was unable to clear the 50 percent threshold in the race, triggering a runoff election against a fellow Democrat in April. M. Spencer Green/AP hide caption

itoggle caption M. Spencer Green/AP

Rahm Emanuel, campaigning for mayor, greets Chicago commuters early this morning. Polls close at 7 pm Central. Scott Olson/Getty Images hide caption

itoggle caption Scott Olson/Getty Images