The Commodity Futures Trading Commission held hearings in the summer on limiting the investments in commodity index funds, and the Obama administration’s choice to lead the commission was in favor of following through.

But the new chairman, Gary Gensler, needs two others on the five-member commission to join him, and this no longer appears likely.

“They have run into roadblocks,” said Tyson Slocum, head of the energy project at the consumer group Public Citizen, who testified at the hearings. “It’s disappointing.”

The index funds buy and sell huge numbers of contracts for future delivery of commodities, mainly oil. This allows investors to benefit from rising commodity prices without ever having to take possession of the commodities.

But the funds also pump billions of dollars into the commodity markets, which consumer groups and several energy-dependent industries said inflated oil and gasoline prices.