DES MOINES - Launching a massive eight-day bus tour in advance of Iowa's first-in-the-nation presidential caucuses, Illinois Senator Barack Obama offered what campaign aides described as a sharpened stump speech today, calling on Iowans to "stand for change." Evidencing the tightness of the Democratic race, Obama mixed his usual optimistic, at times lofty rhetoric with barely veiled attacks on former North Carolina Senator John Edwards and New York Senator Hillary Clinton, his two chief rivals for the nomination.

Ten months after kicking off his campaign, which he called an "unlikely journey to change America," Obama's closing argument is largely the same as those he has made before. But intermixed with a standard stump speech were new attacks on his opponents. "There are others in this race who say that this kind of change sounds good, but that I'm not angry or confrontational enough to get it done," Obama said, referring to recent criticism from Edwards. "I'm the only candidate in this race who hasn't just talked about taking power away from lobbyists, I've actually done it."

Defending himself from Edwards' criticism, Obama saved his harshest words for Clinton, with whom he has been locked in a back-and-forth struggle for supremacy in Iowa polls. "You can have the right kind of experience and the wrong kind of experience," Obama said, responding to charges that he is unprepared. "Mine is rooted in the real lives of real people, and it will bring real results if we have the courage to change. I believe deeply in those words. But they are not mine. They were Bill Clinton's in 1992, when Washington insiders questioned his readiness to lead."

Obama, whose campaign has long stressed various forms of change as a key rationale for his run, joked that in the last few weeks other campaigns are following his successful strategy. "It must be catching on because in these last few weeks everyone's talking about change," he laughed.

Politics, though, does not always run on a predictable script, and Obama took time to pause and remember former Pakistani Prime Minister Benazir Bhutto, who died today in a suicide bombing. "She was a respected and resilient advocate for democracy for the people of Pakistan," Obama said. "We stand with the people of Pakistan in their quest for democracy and against the terrorists that threaten the common security throughout the world."

Obama's "Stand for Change" tour is scheduled to hit twenty-three cities before caucus time. Kicking the tour off in Des Moines, former Air Force Chief of Staff Tony McPeak, introducing the Senator, said it was Obama's fifteenth stop in Des Moines this year. The bus tour includes two more stops in the capitol city, along with swings to eastern and northern cities in the state.