According to Roll Call:

After days of castigating Republicans for allegedly stalling a veterans benefits package, Senate Majority Leader Harry Reid (D-Nev.) himself decided to postpone the start of the debate — and, indeed the start of Wednesday’s session — until 5 p.m. in order to accommodate the schedules of his party’s presidential hopefuls, Democratic sources said.

Reid was joined by Senator Dick Durbin (D-IL) in criticizing Republicans for any potential delays.  And then who actually causes the delays?  Politics…you gotta be disgusted by it.