Huma Abedin, one of Democratic presidential candidate Hillary Clinton's top aides, is separating from husband Anthony Weiner after a sex scandal similar to an earlier incident that led him to resign from the US Congress.
Ms Abedin's announcement comes after a report emerged that he had allegedly exchanged sexual photos with a woman.
He appeared to have sent a photo of himself in his underwear - one with his toddler son nearby.
The former congressman resigned in 2011 after texting explicit photos to women.
"After long and painful consideration and work on my marriage, I have made the decision to separate from my husband," Ms Abedin said in a statement.
"Anthony and I remain devoted to doing what is best for our son, who is the light of our life. During this difficult time, I ask for respect for our privacy."
Ms Abedin is one of Mrs Clinton's most trusted advisers and Republican Donald Trump said the story demonstrated a lack of judgement on Mrs Clinton's part.
"I only worry for the country in that Hillary Clinton was careless and negligent in allowing Weiner to have such close proximity to highly classified information."
The New York Post reported that Mr Weiner had sent sexual messages and half-dressed photos of himself to an unidentified woman in 2015.
One image appeared to show a child next to Mr Weiner, who was in his underpants.
The photos were part of a months-long exchange between Mr Weiner and the woman and many of the messages were sexual in nature, according to the New York Post report.
Mr Weiner resigned from Congress in 2011 and publicly apologised sexting scandal in which he accidentally posted an explicit photo of himself on his public Twitter timeline instead of via a direct message to a woman, as he had intended.
When he made a second unsuccessful run for New York City mayor, explicit photos surfaced in July 2013 that he had recently sent under the pseudonym "Carlos Danger" to a young woman in Indiana.
At the time, Ms Abedin defended the decision to remain by her husband's side, saying it was "made for me, for our son, and for our family".
The former Congressman said he had undergone therapy after the first sexting scandal, according to media reports. In recent months, he has taken care of the couple's toddler son. Ms Abedin often travels with the Clinton campaign.
Weiner, a documentary released in May, followed the politician's failed mayoral bid and his strained marriage in the wake of revelations that he had again been exchanging messages with other women.
Ms Abedin first worked for Hillary Clinton in the 1990s as an intern when Mrs Clinton was first lady. She was a personal aide to Clinton during her successful 2000 campaign for US Senate, worked on Clinton's first, unsuccessful White House bid in 2008 and served as her deputy chief of staff at the US State Department. She is now the vice chair of Clinton's presidential campaign.
- BBC / Reuters