The man who struck US House Speaker Nancy Pelosi's husband on the head with hammer is facing charges of attempted murder and other felonies.
Police have not offered a motive for Friday's assault on Paul Pelosi, 82, who according to his wife's office had surgery for a skull fracture and injuries to his hands and right arm.
Doctors expect a full recovery, Reuters reported.
President Joe Biden, speaking to reporters in Delaware on Saturday, said the attack appeared to have been “intended for Nancy”.
Ms Pelosi said Saturday she and her family were “heart-broken and traumatised” by the attack at their California home.
An intruder had broken into the couple's house in San Francisco on Friday morning and attacked Mr Pelosi with a hammer, fracturing his skull.
“Our children, our grandchildren and I are heart-broken and traumatised by the life-threatening attack on our Pop,” Ms Pelosi said of the incident in a letter posted to Twitter on Saturday evening.
“We are grateful for the quick response of law enforcement and emergency services, and for the life-saving medical care he is receiving,” she said, in her first comment about the attack.
Mr Pelosi was at home alone, as his wife was working in Washington.
“His condition continues to improve,” Ms Pelosi said in the letter.
The incident stoked fears about political violence less than two weeks before midterm elections on November 8 that will decide control of the House of Representatives and Senate.
The House Speaker Ms Pelosi, 82, a Democrat who is second in the constitutional line of succession to the US presidency, flew to San Francisco hours after the attack to be with her husband.
Earlier in the day, Paul Pelosi Jr, the couple's son, was seen outside Zuckerberg San Francisco General Hospital, where his father, a real estate and venture capital executive, was being treated.
Asked by a reporter for an update on his father, he replied: “So far, so good.”
Police named the man arrested at the scene as David DePape, 42.
He, too, was taken to a San Francisco hospital, but it was not made clear whether he was there for medical or psychiatric care or both.
Online sheriff's records showed he was booked into custody on suspicion of attempted murder, assault with a deadly weapon, elder abuse, battery, burglary, threatening a public official or family member, and other felonies.
Formal charges will be filed on Monday, and his arraignment is expected on Tuesday, according to the San Francisco district attorney's office.
San Francisco Police Chief William Scott told a Friday night news briefing that detectives, assisted by FBI agents, had yet to determine what led to the home invasion but said, “We know this was not a random act.”
The intruder shouted, “Where is Nancy?” before attacking, a person briefed on the incident told Reuters.
