(CNN) - It didn't take long for the zings to begin in the closely watched Massachusetts Senate race between GOP Sen. Scott Brown and leading Democratic candidate Elizabeth Warren.
When asked Tuesday at a primary debate how Warren paid for college - noting a nearly nude 1982 Cosmopolitan magazine photo shoot that Brown did to earn money at age 22 - the Democratic candidate fired off: "I kept my clothes on."
Two days later, Brown had one comment about Warren not taking off her clothes.
"Thank God," he said, laughingly, during a radio interview with WZLX in Boston Thursday. "I didn't go to Harvard. I went to the school of hard knocks, and I did whatever I had to do to pay for school."
Brown, who was elected to the Senate in a January 2010 special election, received his degrees from Tufts University and Boston College Law School. Warren graduated from the University of Houston and Rutgers School of Law.
Warren, a Harvard law professor, will face a crowded field of candidates in next year's Democratic Senate primary. She's known for previously serving as a special adviser to President Barack Obama to help develop the recently-formed U.S. Consumer Financial Protection Bureau.
A poll released Monday showed the two candidates in a statistical dead heat.