Washington (CNN) Rob Porter resigned from his White House role this week following allegations of past domestic abuse, and sources told CNN that senior aides to President Donald Trump had known about the allegations for months.

Typically, political appointees brought in with each presidential administration undergo a series of checks to ensure they're fit for the position. This vetting includes background checks, applications for security clearances and ethics reviews -- in hopes that any red flags in their backgrounds won't come as a surprise to the administration or become embarrassing politically.

Here's a look at some other notable Trump administration staff members who stepped down or withdrew their names from consideration because of issues in their résumés or past actions.

Michael Flynn, national security adviser

WASHINGTON, DC - DECEMBER 01: Michael Flynn, former national security advisor to President Donald Trump, leaves following his plea hearing at the Prettyman Federal Courthouse December 1, 2017 in Washington, DC. Special Counsel Robert Mueller charged Flynn with one count of making a false statement to the FBI. (Chip Somodevilla/Getty Images)