His planned departure from President Donald Trump's inner circle is a major downfall for the Harvard graduate and Rhodes scholar, who though mostly unknown, was a big part of the administration.
As staff secretary, Porter spent a lot of time with the President, and traveled aboard Air Force One several times, including during last month's trip to the World Economic Forum in Davos
. He played a crucial role in determining what papers reach the President's desk, a gatekeeping position that meant direct access to Trump.
Porter not only controlled the flow of information onto Trump's desk, but as a lawyer, he also helped vet the mountain of documents that require the President's signature.
Years of experience
Prior to joining the White House staff, Porter worked for other GOP leaders behind-the-scenes.
He served as chief of staff to Sen. Orrin G. Hatch, a Republican from Utah. His former boss issued a statement Wednesday following the allegations.
"In every interaction I've had with Rob, he has been courteous, professional, and respectful," Hatch said.
"My staff loved him and he was a trusted adviser. I do not know the details of Rob's personal life. Domestic violence in any form is abhorrent and unacceptable."
When Porter got his job at the White House, Hatch described him as an "inspired" pick, saying his move to Washington is a loss for him but a gain for the President.
"Rob is not only a brilliant leader, he is also a dear friend and a trusted confidante who has my full confidence and support," he said at the time.
A few months after he started working for Hatch, he got promoted to chief of staff
Porter's rise in politics was not entirely a surprise.
His father, Roger Porter, worked for several White House administrations before becoming a professor at Harvard.
"Combining both their tenures, the father-son duo has advised nearly every Republican administration since Gerald Ford," Utah's Deseret News
said in an Opinion piece last year.
It described the younger Porter as "level-headed, hyper-competent Republican pragmatist."
In a chaotic White House where eye-popping headlines are the order of the day, Porter has largely stayed out of the media spotlight -- until now.
White House Chief of Staff John Kelly viewed him as a right-hand man who would impose his system of order in his absence.
That may explain why Trump's senior aides, who multiple sources say knew for months about the ex-wives' allegations, took no action to remove him from the staff.
At first, Kelly defended Porter as "a man of true integrity and honor." But by Wednesday evening, Kelly issued a new statement.
"There is no place for domestic violence in our society. I stand by my previous comments of the Rob Porter that I have come to know since becoming Chief of Staff, and believe every individual deserves the right to defend their reputation," he said.
Porter's ex-wives detailed the allegations to the FBI when it conducted its routine background check on him. A year into the administration, Porter does not hold a security clearance
Colbie Holderness and Jennifer Willoughby, his first and second wives respectively, said his consistent abuse led to their respective divorces.
Holdnerness married Porter in 2003, and told CNN on Wednesday that the physical abuse began almost immediately. The couple went to the Canary Islands for their honeymoon, where Porter kicked her thigh during an argument, she said.
She alleged that Porter's repeated physically abusive behavior included throwing her on the bed, choking her and forcefully pushing one of his limbs into her body. During a trip to Italy, she said he punched her in the face.
Willoughby married Porter in 2009, and told CNN she endured emotional abuse from Porter that included "intense" bursts of anger.
Porter issued a strong statement denying the allegations.
"These outrageous allegations are simply false," he said. "I have been transparent and truthful about these vile claims, but I will not further engage publicly with a coordinated smear campaign."
Porter's last day at the White House
has not yet been set.