Senator Ed Markey is widening his lead over Representative Seth Moulton. 

A UMass Amherst/WCVB poll of 445 primary voters gives Markey 60-percent and Moulton 32-percent.  Markey led 51-percent to 28-percent in polling last October. 

Pollsters say Markey supporters favor his progressive record, while Moulton supporters cite his younger age. 

The candidates will debate from 8 to 9 p.m. on Thursday ahead of the September 1st primary.