The Fourth of July is just days away, and on the Loop's crowded streets and plazas, outside the downtown campus of the University of Chicago Graduate School of Business, the city swelters. Upstairs, in an air-conditioned office, Austan Goolsbee is recounting how he was transformed from an economics professor into the senior economic advisor to a candidate for the presidency of the United States.

Goolsbee must pick his words more carefully now, but it's no great strain for him to tell a good story. The two men met in 2004, after Barack Obama became the Democratic contender for junior U.S. senator from Illinois and the Republicans fielded the perennial candidate Alan Keyes. Though Keyes's Christian Dominionist views on government and society have long made him unelectable, the Democrats wanted to ensure that Obama could demolish the opposition's economic platform. So his campaign contacted Goolsbee, whom Obama knew by reputation, from his own years teaching constitutional law at the University of Chicago, as an expert on much that was cutting-edge in economics.