For all the excitement Mr. Obama's potential candidacy has stirred, he remains a 45-year-old first-term senator who is largely untested in national politics. Yes, Mr. Obama is unusually talented, Democrats and Republicans alike say, but the history of presidential campaigns is filled with examples of celebrity candidates like Gen. Wesley Clark in 2004 who burst onto the political stage but eventually sputtered as they struggled to master the difficulties of running for president.
UpdateNoam Scheiber