This story was updated at 3 p.m. ET
Two top staffers for Ben Carson's presidential campaign have resigned, an ominous sign for the struggling Republican's White House hopes just a month before voting begins.
Campaign manager Barry Bennett and communications director Doug Watts have both stepped down, something the campaign called "enhancements" to "shift the campaign into a higher gear."
Retired Army Major General Bob Dees will take over as campaign trail while Ed Brookover, former a senior strategists, will be the new campaign manager.