The top U.S. derivatives regulator may dwindle to just two voting commissioners and will struggle to approve new rules unless the White House and Senate can overcome political hurdles to fill the vacancies by the end of the year, Bloomberg News reported today. The Commodity Futures Trading Commission (CFTC), which is designed to have five members regulate trading by banks including Goldman Sachs Group Inc. and JPMorgan Chase & Co., could instead have only one Democrat and one Republican early next year. The split would probably delay votes on contentious Dodd-Frank Act regulations. The possible gridlock comes as the agency tries to flex its powers under the 2010 Dodd-Frank Act, which gave the commission oversight of the $633 trillion swaps market after largely unregulated trades helped fuel the credit crisis.