Campaigning For Key Primaries

Sen. Hillary Rodham Clinton, D-N.Y., and Sen. Barack Obama, D-Ill., speak during their debate Tuesday, Feb. 26, 2008, in Cleveland ahead of key primaries in Ohio and Texas. The Ohio and Texas primaries typically come well after the nominee is decided. But as Obama and Clinton have remained in a tight race for nominating delegates, the two contests are critical. Rhode Island and Vermont also hold primaries Tuesday.

Democratic presidential hopeful, Sen. Hillary Rodham Clinton, D-N.Y, visits with supporters as she campaigns at Herrera's Mexican Cafe in Dallas, Tuesday, March 4, 2008, the day of the Texas presidential primary election.

Democratic presidential hopeful Barack Obama greets Kasey Jeffries, 17, an agriculture mechanic participant from Latexo, Texas, at the Houston Livestock Show and Rodeo as Obama made some last-minute campaign stops Tuesday, March 4, 2008, in Houston.

Republican presidential hopeful, Sen. John McCain, R-Ariz., and his wife Cindy, right, arrive at a campaign stop at the Mi Tierra Restaurant in San Antonio, Texas, Tuesday, March 4, 2008.

Supporters for various different candidates stand behind Republican presidential hopeful, former Arkansas Gov. Mike Huckabee as he does a television interview at a voting location in Dallas, Tuesday, March 4, 2008.

Democratic presidential hopeful Sen. Hillary Rodham Clinton, D-N.Y., speaks during a rally Monday, March 3, 2008, in Austin, Texas.

Democratic presidential hopeful Sen. Barack Obama, D-Ill., makes remarks during a rally Monday, March 3, 2008, in Houston.

Democratic presidential hopeful Sen. Hillary Rodham Clinton, D-N.Y., center, is cheered by the crowd as she arrives at a rally Monday, March 3, 2008, in Austin, Texas.

Supporters cheer for Democratic presidential hopeful Sen. Barack Obama, D-Ill., during a rally Monday, March 3, 2008, in Houston.

Former U.S. President Bill Clinton campaigns for his wife, Democratic presidential hopeful Sen. Hillary Clinton, D-N.Y., during a campaign stop at the El Paso International Airport, Monday night March 3, 2008 in El Paso, Texas.

Democratic presidential hopeful Sen. Barack Obama, D-Ill., and his wife Michelle wave to the crowd during a rally Monday, March 3, 2008, in Houston.

Democratic presidential hopeful, Sen. Hillary Rodham Clinton, D-N.Y, makes a campaign stop at the Austin Convention Center in Austin, Texas, Monday, March 3, 2008. Seated right on the stage is actress Eva Longoria.

Democratic presidential hopeful Sen. Barack Obama, D-Ill., greets supporters at a rally Monday, March 3, 2008 in Houston.

Nine-month-old Rylee Ferguson is held by her mother Miranda Ferguson as they wait for Democratic presidential hopeful, Sen. Hillary Rodham Clinton, D-N.Y, to sign a photo of former President Bill Clinton during a campaign stop at an airport hanger at the Beaumont, Texas, Airport Monday, March 3, 2008.

Democratic presidential hopeful Sen. Barack Obama, D-Ill., holds a baby as he works the rope line following his address during a rally Monday, March 3, 2008, in Houston.

Democratic presidential hopeful, Sen. Hillary Rodham Clinton, D-N.Y, signs autographs as she is assisted by her traveling chief of staff Huma Abedin during a campaign stop at the Austin Convention Center in Austin, Texas, Monday, March 3, 2008.

A supporter holds an old magazine featuring Democratic presidential hopeful, Sen. Hillary Rodham Clinton, D-N.Y, during Clinton's campaign stop at the Student Union Auditorium at the University of Toledo, in Toledo, Ohio, Monday, March 3, 2008.

Supporters of Barack Obama wave signs in Essex Junction, Vt., Monday, March 3, 2008. Vermont is the smallest of the four states holding Democratic primaries Tuesday in the closest presidential nominating contest in years.

Hannah Donovan, rear, is joined by young relatives to campaign for Hillary Clinton in Burlington, Vt., Monday, March 3, 2008. From left front are Norah Mitchell, Delia Donovan and Lilly Mitchell.