U.S. Securities and Exchange Commission Chairman Mary Schapiro faced skeptical lawmakers from both parties today as she defended her campaign to overhaul the regulation of money-market funds.

In an appearance before the Senate Banking Committee that lasted just under an hour, Schapiro told lawmakers that while most funds are "well and responsibly managed," they are susceptible to the types of runs that helped freeze credit markets in 2008. Schapiro hasn't been able to convince a majority on her five-member commission to support a proposal to rewrite money-market rules and today's hearing demonstrated the difficult task she faces on Capitol Hill as well.

"In my view, you're portraying an industry that's extremely vulnerable, that has all these risks of runs and I really find that extraordinary in light of the actual history," Senator Patrick Toomey, a Pennsylvania Republican, told Schapiro. "We've had another round of real stress: an ongoing recession, European credit crisis, downgrade of the U.S. government, considerable redemption pressure and not a single problem in this industry."