Democratic big wigs are attempting to corral A-list celebs to show face at the Democratic National Convention -- and one person we know they've locked down is John Legend.
Sources with direct knowledge tell TMZ ... John is all in for an appearance at the convention in Chicago in a few weeks -- and while we know he's going to be participating front and center ... it's still a little hazy on how exactly he'll contribute.
HANGING ON EVERY WORD
In other words .