Polar bear tug of war Environmentalists want the polar bear to be the first animal placed on the endangered species list due to global warming. Objectors say the move is politically motivated, and may hurt the petroleum industry.9:06 a.m.
Mark Serreze: Senior research scientist at the National Snow and Ice Data Center.
Robert J. Smith: Adjunct scholar in environmental policy at Competitive Enterprise Institute.
Wisconsin up for grabs Wisconsin voters go to the polls today for that state's presidential primaries, and 74 convention delegates at stake. Will Wisconsin's historically independent voters keep the momentum going for Barack Obama, or provide Hillary Clinton with the spark she needs to reignite her campaign?9:45 a.m.
Thomas Holbrook: Wilder Crane Professor of Government at the University of Wisconsin-Milwaukee.
Lynne Cox: swimming the cold seas She swam the English Channel as a teenager. In 1987, she crossed the Bering Strait between the Soviet Union and Alaska. Her toughest feat: swimming for 25 minutes near Antarctica in water cold enough to kill in much less time. In the rarified world of distance cold water swimming, Lynne Cox is the best known. She's also the author of two books on her adventures.10:06 a.m.
Lynne Cox: Open water swimmer and author. Her books include "Swimming to Antarctica" (2004) and "Grayson," just out in paperback.