The first-term senator, a former Harvard Law professor, also said in the People interview released Wednesday that if there's any lesson I've learned in the last five years, it's don't be so sure about what lies ahead. Warren has been a leading voice in the Senate on curbing Wall Street excess, allowing college students to refinance their loans and protecting Social Security and Medicare. The senator has played an active role on the campaign trail this year, helping fellow Democrats like Minnesota Sen.