There are many criteria that can be used to determine which presidential debate moderator performed best, including the number of questions asked, the quality of the questions, as well as any perceived biases toward the candidates. And of course some candidates are in need of more moderating than others.
But perhaps the most basic measure is which one spoke for the least amount of time, because the less we hear from the moderators, the more we hear from the candidates.
Here's a breakdown of how much time each moderator spoke. I include all the time the moderators spent talking from the moment the candidates appeared until the moderators signed off. I include not only time spent asking questions but also interruptions and cross-talk involving the moderator. All the debates lasted 90 minutes.
Jim Lehrer (First Presidential Debate): 7 minutes 55 seconds
Bob Schieffer (Third Presidential Debate): 8 minutes 27 seconds
Candy Crowley: (Second Presidential Debate): 9 minutes 40 seconds
Martha Raddatz (Vice Presidential Debate): 12 minutes 28 seconds
The second presidential debate deserves an asterisk because audience members asked many of the questions, and I included the time they took to ask their questions in Candy Crowley's total.
A few seconds here or there may not seem all that important. But the debates are the only chance voters get to hear directly from the candidates in an unscripted forum, to watch them interact, and to compare and contrast their policy prescriptions. Every second counts.