At least four senior staffers were among the Republican National Committee employees who were terminated Monday as the Trump campaign brass more formally took the reins of the RNC, according to two sources familiar with the matter.

One of the key staffers to depart was Elliot Echols, the RNC’s political director.

The RNC met in Houston last week to install a pair of new leaders selected by Trump: Chairman Michael Whatley, who previously led the North Carolina Republican Party, and Trump’s daughter-in-law Lara Trump as co-chair. Former RNC chair Ronna McDaniel agreed to step down last month after Trump formally endorsed Whatley.

Chris LaCivita, a Trump co-campaign manager, stepped into the role of chief operating officer at the RNC on Monday. He hired Sean Cairncross, who led RNC operations from 2015 to 2016, as his deputy.

LaCivita will be involved with the two merged operations from Washington, D.C., and from the campaign trail.

Cairncross sent a staffwide email Monday indicating that Whatley had directed a staffing assessment, according to a source familiar with the matter, and that some employees would be asked to resign and reapply.

According to a copy of the email obtained by NBC News, the evaluation is intended “to ensure the building is aligned with his vision of how to win in November.”

“During this process, certain staff are being asked to resign and reapply for a position on the team,” the email reads.

The finance and digital operations are expected to be spared, while as many as 60 RNC staffers could be affected by the terminations, the source said.