Clay Aiken is proving to be the most successful loser in history. The American Idol runner-up's debut CD, Measure of a Man, entered Billboard's album chart at No. 1 with sales of 613,000 copies. By comparison, Idol's inaugural champ, Kelly Clarkson, moved 297,000 units during her album's first week in stores last April. Now, the pressure's on Aiken's Idol sidekick Ruben Studdard, whose Soulful CD drops Nov. 25.