Police block protestors outside the venues for the Democratic National Convention (DNC) in Charlotte, North Carolina, the United States, Sept. 4, 2012. U.S. President Barack Obama is to be named the Democratic Party's nominee during the DNC, which is scheduled to be held from Sept. 4 to Sept. 6. (Xinhua/Zhang Jun)

Police block protestors outside the venues for the Democratic National Convention (DNC) in Charlotte, North Carolina, the United States, Sept. 4, 2012. U.S. President Barack Obama is to be named the Democratic Party's nominee during the DNC, which is scheduled to be held from Sept. 4 to Sept. 6. (Xinhua/Zhang Jun)

Police block protestors outside the venues for the Democratic National Convention (DNC) in Charlotte, North Carolina, the United States, Sept. 4, 2012. U.S. President Barack Obama is to be named the Democratic Party's nominee during the DNC, which is scheduled to be held from Sept. 4 to Sept. 6. (Xinhua/Zhang Jun)

Police block protestors amid a downpour outside the venues for the Democratic National Convention (DNC) in Charlotte, North Carolina, the United States, Sept. 4, 2012. U.S. President Barack Obama is to be named the Democratic Party's nominee during the DNC, which is scheduled to be held from Sept. 4 to Sept. 6. (Xinhua/Zhang Jun)

Police watch as protestors march to the venues for the Democratic National Convention (DNC) in Charlotte, North Carolina, the United States, Sept. 4, 2012. U.S. President Barack Obama is to be named the Democratic Party's nominee during the DNC, which is scheduled to be held from Sept. 4 to Sept. 6. (Xinhua/Zhang Jun)

A protestor holds a placard outside the venues for the Democratic National Convention (DNC) in Charlotte, North Carolina, the United States, Sept. 4, 2012. U.S. President Barack Obama is to be named the Democratic Party's nominee during the DNC, which is scheduled to be held from Sept. 4 to Sept. 6. (Xinhua/Zhang Jun)

Protestors march pass a bus stop outside the venues for the Democratic National Convention (DNC) in Charlotte, North Carolina, the United States, Sept. 4, 2012. U.S. President Barack Obama is to be named the Democratic Party's nominee during the DNC, which is scheduled to be held from Sept. 4 to Sept. 6. (Xinhua/Zhang Jun)

Police arrest a protestor outside the venues for the Democratic National Convention (DNC) in Charlotte, North Carolina, the United States, Sept. 4, 2012. U.S. President Barack Obama is to be named the Democratic Party's nominee during the DNC, which is scheduled to be held from Sept. 4 to Sept. 6. (Xinhua/Zhang Jun)