If history is any guide, President Obama's Cabinet is in line to lose at least one of its top energy and environmental members should he win a second term this fall. Two of the 20 leaders at U.S. EPA, the Energy Department and the Interior Department under the nation's three most recent two-term presidents hold the distinction of staying on board for all eight years. One question that looms while Obama gears up for a hard-fought re-election battle, then, is whether Lisa Jackson, Steven Chu and Ken Salazar will enter the history books as a Carol Browner or Bruce Babbitt -- Clinton-era Cabinet officials who stayed the course -- or join the 18 others who departed sometime before the end of the second term.