The five major Democratic candidates in the May 15 mayoral primary are to debate twice in the next two nights.

  • Today: 8 p.m. on WHYY TV12 and WHYY-FM (90.9) with host Marty Moss-Coane. The debate, at the WHYY Technology Center, is sponsored by The Next Mayor, a joint effort of the Committee of Seventy, the Philadelphia Daily News and WHYY.

  • Monday: 7 p.m. on NBC10 with host Chris Matthews. The debate, at the National Constitution Center, is sponsored by the center, the Philadelphia Tribune, WHYY and NBC10.