The husband of US House of Representatives Speaker Nancy Pelosi has been "violently assaulted" after a break-in at their California home.
Paul Pelosi, 82, was taken to hospital and is expected to make a full recovery, a spokesperson said.
The suspect, who has not been named, is in custody but the motive for the attack is unclear.
Mrs Pelosi was not at the San Francisco residence when the incident took place on Friday morning.
"The Speaker and her family are grateful to the first responders and medical professionals involved, and request privacy at this time," a spokesman for the senior Democrat said.
The assailant used a hammer to gain entry to the home, two sources told CBS News, but it is unclear if it was used to attack Mr Pelosi.
Mrs Pelosi is one of the most powerful politicians in the country. She was re-elected to a fourth term as Speaker of the House of Representatives in 2021, making her second in line to the presidency after Vice-President Kamala Harris.
The Baltimore native has represented the San Francisco area in Congress since 1987, and typically splits her time between California and Washington.
She is currently fundraising and campaigning with Democrats around the country ahead of the midterm elections on 8 November, and was in Washington with her security detail at the time of the attack on Friday.
Her husband, the multimillionaire founder of a venture capital firm, resides primarily in San Francisco where he was born and raised.
The couple have been married since 1963 and have five children. Their combined net worth, primarily from Mr Pelosi's investments, has made the speaker one of the richest members of Congress.
The exact circumstances of the attack are unclear and it is not known how the intruder entered the couple's residence.
The FBI and the US Capitol Police, which has a field office in California, are assisting San Francisco police with the investigation.
Members of Congress have been on high-alert over security threats since last year's riot at the US Capitol. Mrs Pelosi's office in the building was ransacked by supporters of then-President Donald Trump during the attack.
And last year, her San Francisco home was reportedly vandalised with graffiti saying "cancel rent".
Senior Republicans, such as Senate Leader Mitch McConnell, have also been targeted by vandalism in recent times.