Morning Buzz: March 8, 2007

This morning's top stories:

• President Bush leaves for a five-country tour of Latin America today, intent on bolstering U.S. influence at a time when Venezuelan President Hugo Chavez's sway in the region is on the rise.
• Democrats in the House are pushing legislation that would require a withdrawal of troops from Iraq by the fall of 2008, the AP reports. Meanwhile, the new commander in Iraq said today that insurgent attacks are intensifying.
• Bush indicated Wednesday that a pardon of former Cheney aide "Scooter" Libby is unlikely in the near future, the Washington Post reports.
• An Indian tribe in Arizona has constructed a giant glass-bottomed walkway along the edge of the Grand Canyon, hoping to attract tourists -- and and their money -- to the area.