(CNN) - At a large Democratic event in Iowa, Sen. Barack Obama finally delivered on weeks of promising to get tough on Sen. Hillary Clinton, one of Obama's chief rivals for the 2008 Democratic presidential nomination. At the same event, former Senator John Edwards also had strong words. Not to be outdone, Clinton and her supporters responded with rallying cry to "turn up the heat" in Clinton's bid for the White House. Watch Jessica Yellin's report.
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