Almost simultaneously with the announcement that Mary Schapiro was stepping down as SEC chairman, the White House issued a statement from President Obama designating current SEC commissioner Elisse Walter as the new SEC chairman. "I'm confident that Elisse's years of experience will serve her well in her new position, and I'm grateful she has agreed to help lead the agency," President Obama said.

Interestingly, the White House statement did not characterize Walter as an "interim" or "acting" chairman, which led to some initial speculation that Walter might be the White House's pick to be the long-term successor to Schapiro. A White House official later clarified, however, that President Obama plans to separately nominate a long-term replacement "soon." Walter could still be among those considered for the long-term role, along with several others.

Walter's 5-year term as an SEC commissioner actually already expired on June 5, 2012.  SEC commissioners may legally serve beyond their term, however, through the end of the next session of Congress (i.e., until December 2013). This provides the White House with a good bit of time to select a successor and have that person approved by the Senate.

What should investors expect from Walter as SEC Chair? Some SEC watchers say that Walter and Schapiro have been close friends who are "joined at the hip" in terms of their experience and orientations. Reuters reports that with just one exception, Walter voted for all of the regulations championed by Schapiro. According to former SEC official Thomas Sporkin, Walter is likely to continue to pursue the Schapiro agenda. "Essentially you are handing off the mantle to somebody who has the same agenda," Sporkin told Reuters.

Until a new commissioner is named to replace Schapiro, the SEC will operate with just four commissioners--two Democrats and two Republicans. This could make it difficult for the SEC to get a majority vote on any contentious reforms that Walter may want to implement.