Rob Porter's not the only one - the Trump White House has been plagued by people not getting security clearances

AP Photo/Pablo Martinez Monsivais

Rob Porter, left, White House Staff Secretary speaks to President Donald Trump after Trump made remarks regarding the on going situation in Charlottesville, Va., Saturday, Aug. 12, 2017 at Trump National Golf Club in Bedminister, N.J. Porter reminded Trump that he still needed to sign the Veteran's Affairs Choice and Quality Employment Act of 2017.

Rob Porter resigned at White House staff secretary on Wednesday after his two ex-wives went public with allegations that he abused them during their marriages.

The Intercept reported earlier that day that the FBI had spoken with both women about their allegations during background interviews about Porter. Those allegations reportedly contributed to the year-long delay in granting him the security clearance customary for staffers of his rank.

But Porter is far from the only Trump administration official to encounter problems or controversy over his security clearance. Democrats have been pressing the White House to provide details on its security clearance process, and lawmakers repeated that call on Thursday in the wake of Porter's resignation.

It's unclear how many White House staffers have been delayed permanent security clearance due to red flags raised during their FBI background checks, and deputy press secretary Raj Shah declined to answer when a reporter asked him for specific details during Thursday's press briefing.

But there are several top officials whose security clearances have been revoked - or at least heavily questioned by critics and the media.

Here are the figures who have come under fire: