The departure of Supreme Court Justice John Paul Stevens adds a crucial task to the Senate schedule, at a minimum, and could peel momentum from looming climate legislation if his successor triggers a searing political fight.

Stevens' announcement arrived more than a week before the anticipated release of a Senate bill restricting greenhouse gases. That timing clouds the chamber's legislative horizon by handing senators a top White House priority in the months leading to contentious midterm campaigning.

That leaves climate change -- still competing for attention with Obama's other big priorities, like an overhaul of Wall Street and a comprehensive jobs bill -- in limbo. The climate bill being drafted by Sens. John Kerry (D-Mass.), Lindsey Graham (R-S.C.) and Joseph Lieberman (I-Conn.) would need to gain swift support to outpace the encompassing confirmation of a life-serving justice, according to some observers.

There's a stretch of time between two congressional recesses, Memorial Day and the Fourth of July, that provides an optimal window for movement of a bill, said Chelsea Maxwell, a former climate adviser to retired Sen. John Warner (R-Va.). That gives lawmakers an opportunity to bring legislation to the Senate floor before the height of the election season and any political maneuvering over a Supreme Court nominee.