The Securities and Exchange Commission has announced the departure of four key staff members since the Nov. 4 presidential election. SEC Chief Accountant Conrad W. Hewitt announced his plan to leave last week. John White, director of the Division of Corporation Finance, announced his departure two days after the election. Brian Cartwright, general counsel, and Alexander Cohen, deputy chief of staff, are also leaving. Though his term on the commission does not end until 2010, SEC Chairman Christopher Cox is expected to resign after President-elect Barack Obama names his successor as chairman.