When Mary Schapiro steps down as chairman of the U.S. Securitiesand Exchange Commission this week, she'll leave behind a commissioncomposed of two Democrats and two Republicans — an even split thatcould drag an already sluggish agency to a standstill.

Dozens of rules could run aground, including the so-calledVolcker rule to limit risky trading by deposit-holding banks,restrictions on executive pay, a ban on conflicts of interest inasset-backed securities and swaps-market regulations.

“The issues that they're dealing with are divisive issues thathaven't lent themselves to consensus,” said Barbara Roper, directorof investor protection for the Washington-based Consumer Federationof America. “It becomes all but impossible on a commission divided2-2.”