When a meltdown on Wall Street threatened the financial system in 1998, Gary G. Gensler was still a newcomer at the Treasury Department. He was part of the government team that orchestrated the rescue of Long-Term Capital Management, a big hedge fund that had made bad bets on exotic financial contracts known as derivatives. But once the smoke cleared, Gensler closed ranks with others in the Clinton administration who decided against subjecting derivatives to tighter regulation.

"Looking back now, it's clear we should have done more then," Gensler said in a recent interview.

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