WASHINGTON (CNN) -- Several Republican sources tell CNN that Republican National Committee Chairman Ken Mehlman is all but certain to step down at the end of the year, and the White House already is searching for a replacement or replacements to lead the party into the 2008 presidential campaign cycle.

Two sources, speaking on condition of anonymity, said Mehlman has made clear to close associates for some time he was likely to leave after the 2006 elections -- and that there is no dissatisfaction with his performance in the midterm cycle. A third source confirmed Mehlman's leaving is a good possibility but said a final decision has not been made. "It would be wrong to call it a done deal," this source said.

One name that has come up as a possible replacement is outgoing Maryland Lt. Gov. Michael Steele, who just lost a US Senate race. One of the sources, though, said a more likely scenario is for Steele to join the Bush administration in another capacity after the first of the year when a few members of the Bush Cabinet and other senior officials are expected to leave.

One scenario under discussion, should Mehlman leave, according to two of the sources, is to split the RNC leadership duties, a model both parties have used at times in the past.

Under this approach, a party operative would be brought in to run day-to-day affairs, and a prominent Republican, most likely a former office holder, would be named general chairman. The name most talked about to run the day-to-day operation in such an approach is Maria Cino, a veteran Republican strategist who currently serves as deputy transportation secretary.

-- CNN Chief National Correspondent John King