Sen. Bernie Sanders, who is narrowly leading a pack of Democrats seeking the presidential nomination, lags in support among critical superdelegates who have mostly remained on the sidelines rather than commit to Sanders or any other candidate thanks to the uncertainty of the race.

Superdelegates will play a pivotal role in deciding the party’s presidential nominee if the top candidate fails to win a majority of a separate set of delegates up for grabs in the primaries and caucuses now underway.