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A huge explosion that may have been the work of a homicide bomber ripped through U.N. headquarters (search) in Baghdad. At least 20 people are dead and scores of others have been injured.

Sergio Vieira de Mello (search), one of the highest-ranking officials at the United Nations, was killed by the blast.

Tuesdays with Bill Bennett are back — And Bill will be here to assess the situation in Iraq.

Republican California gubernatorial candidate Bill Simon (search) has launched an anti-Arnold campaign. What will this mean for party unity? Could this actually bolster Gray Davis’s (search) campaign?

California Democratic Party Chair Art Torres and Rep. Dana Rohrabacher, R-Calif., will join the debate.       

And later, U.S. war protestors who went to Iraq to serve as human shields (search) have found themselves facing $10,000 fines. Should they be punished for violating government sanctions against travel to the country?

Ryan Clancy, who went to Iraq (search) before the war, will tell us his story.

Watch Hannity & Colmes LIVE this evening at 9 p.m. ET!

--The Associated Press contributed to this report

-All guests and topics subject to change