After weeks of speculation, President Barack Obama on Tuesday afternoon nominated Timothy Massad, a Treasury Department official, to replace Gary Gensler, the outgoing chairman of the Commodity Futures Trading Commission.

Gensler, who also served at the Treasury Department, during the Clinton Administration, has signaled his intention to step down by the end of the year. With last week’s re-proposal of a position limits rule for commodity trades, the CFTC, under his watch, has nearly completed its share of Dodd-Frank Act mandates. The biggest remaining bit of rulemaking is the controversial Volcker Rule, a restriction on proprietary trading by federally-insured banks. Gensler, according to agency observers and insiders, has urged stronger, more restrictive rulemaking, something other involved agency heads have pushed back against.