The source, who has first-hand knowledge of the information from speaking to campaign officials, also said the campaign has retained the legal firm Butler Snow for unknown reasons.
Sims, a former chief of staff to Mississippi Gov. Phil Bryant, leaves his campaign manager post having won a bitter primary fight against odds but also amid allegations of vote-buying and other improprieties that have engulfed the election's outcome in acrimony.
Noel Fritsch, a spokesman for Cochran's primary challenger Chris McDaniel, who is reviewing ballots for irregularities and has vowed to challenge the election results in court, said the personnel change showed "Cochran's campaign is in a state of wild disarray."
"Sen. Cochran should return to Mississippi and take control of his campaign by addressing the allegations of criminal misconduct surrounding his campaign's strategy of pushing Democrats to the polls on June 24th," Fritsch added.
Cochran's campaign spokesman Jordan Russell has not responded to an emailed request for comment on the matter, and a voicemail left for Davis on Wednesday was not returned. The Clarion-Ledger reported that Sims would stay on the campaign as an adviser.
While it's unclear if Sims resigned, was scheduled to leave already, or was fired, he was named in late June by a Democrat and self-proclaimed pastor the Rev. Stevie Fielder in Meridian, MS, as being part of the Cochran campaign's alleged effort to pay black Democrats cash to vote for Cochran in the runoff.
Fielder, who was paid by freelance journalist Charles Johnson for text messages he exchanged with a contact identified in Fielder's phone as Cochran campaign staffer Saleem Baird, alleges that Cochran's team gave him envelopes of cash to distribute $15 payments to each black voter who would vote for Cochran. Fielder said Baird, Sims, and a woman named "Amanda" discussed the alleged vote-buying scheme with him.
Cochran's campaign has denied the allegations, and several community leaders, including the pastor of his church, cast doubt on his credibility.
Meanwhile, Amanda Shook-another Cochran campaign staffers-has been tied up in another issue with regard to how the Cochran campaign disbursed $53,000 to her in cash as reimbursments for paying campaign workers. F.E.C. regulations do not allow reimbursements to campaign staffers for that purpose, and campaign officials admitted they "screwed up" and would be amending the reports.
Roll Call reported last year that when Cochran was looking for a campaign manager for this cycle, Mississippi political establishment figures lined up to endorse Sims for the job.Roll Call's Kyle Trygstad reported that Sen. Roger Wicker (R-MS)-Sims' father-in-law-and former Gov. Haley Barbour and former Senate Majority Leader Trent Lott each personally called Cochran to encourage him to hire Sims.
"I welcome Kirk Sims to my campaign team, and appreciate his willingness to serve as campaign manager," Cochran said in a statement then. "Kirk has demonstrated a commitment to the interests and the values of the citizens of Mississippi. His background and experience are consistent with my principles. He will be instrumental in the effort to engage and unite the people of our state in a discussion about Mississippi's bright future."
Johnson first reported Sims' replacement as campaign manager.