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Ralph Nader spent the first day of his presidential campaign defending himself against allegations that his candidacy will be a detriment to the Democratic presidential nominee. Jim Lehrer speaks with Nader about the aims of his presidential bid.

The Department of Homeland Security was created last March with the merger of 22 federal agencies and 180,000 employees. Margaret Warner asks Homeland Security Secretary Tom Ridge for a progress report as the first anniversary of the department approaches.

A move by conservative clerics to ban moderate candidates from parliamentary elections has prompted widespread boycotts and thrown the future of Iran's reform movement into doubt. Two Iranian experts assess the impact of Friday's vote.