[cnn-photo-caption image= http://i.l.cnn.net/cnn/2008/POLITICS/03/10/dems.campaign/art.obama.wy.gi.jpg caption="Sen. Barack Obama campaigns in Laramie, Wyoming, over the weekend."](CNN) - Sen. Barack Obama Monday focused on Mississippi, which holds primaries on Tuesday, while Sen. Hillary Clinton keep her eye on the next big prize on the Democratic calendar, Pennsylvania.
Thirty-three delegates are at stake Tuesday, and in the tight Democratic race, every delegate is critical. CNN estimates that Obama leads Clinton by less than 100 delegates, 1,527 to 1,428. A candidate needs 2,024 delegates to win the nomination. Obama won the Wyoming caucuses Saturday, where he picked up seven delegates. Clinton won five delegates.
Obama was scheduled to hold rallies in Columbus and Jackson, Mississippi, while Clinton was set to hold campaign events in Scranton, Pennsylvania. Pennsylvania holds its primary on April 22.