“It was definitely not me,” Northam said at an afternoon news conference. “I can tell by looking at it.”

But within hours, three of the state’s most senior Democrats said they had called Northam to tell him to step down, depriving the governor of his last remaining support and intensifying the pressure on him.

“We no longer believe he can effectively serve as the governor of Virginia and that he must resign,” Sens. Mark Warner and Tim Kaine and Rep. Robert Scott said in a statement.

Addressing reporters in the governor’s mansion, Northam said he had initially acknowledged that it was him in the photograph when it surfaced Friday because he wanted to “take credit for recognizing that this was a horrific photo that was on my page with my name on it.”

He said that after talking on the phone with friends and family in an effort to jog their memories about the photograph, he decided to reverse course, because he concluded that it was not him in the racist attire.

However, he may have made his effort to remain in office more difficult by revealing that, on another occasion, he had darkened his face with shoe polish for a Michael Jackson costume in a dance contest in Texas in 1984, when he was a young Army officer.

“I look back now and regret that I did not understand the harmful legacy of an action like that,” he said.

The governor’s refusal to resign plunged Virginia into political turmoil and created a crisis for national Democrats, who have assailed President Donald Trump for his demagogy on racial issues and have made plain that they cannot abide a prominent party leader associated with emblems of bigotry.

By the time he strode to a lectern in the governor’s mansion Saturday afternoon, with portraits of Virginia’s founding fathers behind each shoulder, Northam was increasingly isolated.

His own state party has abandoned him, its leaders furious that he had not resigned as they expected he would when they went to bed late Friday, according to one high-ranking Virginia Democrat. Top Democratic presidential contenders issued calls for Northam to step down, as did House Speaker Nancy Pelosi.

The governor’s news conference did not appear to change many minds. By the time it concluded, Virginia’s Legislative Black Caucus had reaffirmed its call for the governor to quit.

“It just made matters worse, because he owned it, and now he’s trying to walk it back,” said Charniele Herring, a Democratic state legislator from Alexandria.

Herring, who once headed the state Democratic Party and is African-American, spoke with Northam in the hours after the photograph surfaced and said he should have offered then the version of events he presented Saturday.

“If he had said, that is not me, I wouldn’t have last night joined my colleagues in calling for his resignation,” she said.

Later Saturday, L. Douglas Wilder, Virginia’s former governor and the first black elected governor in the United States, also urged Northam to step down.

If Northam does ultimately resign, Lt. Gov. Justin Fairfax, who is black, would become governor. Fairfax broke his silence after the governor’s news conference but did not directly urge him to stay or go, saying in a statement that “we must make decisions in the best interests of the people of the Commonwealth of Virginia.”

The governor said he had spoken with Fairfax, 39, several times since the yearbook photo emerged. “I plan to continue to lead,” Northam said, before slightly opening the possibility that he could quit. “If we get to the point that we feel we are not effective, we are not efficient,” he said, he would “revisit this.”

That possibility grew far more likely shortly before 7 p.m. Eastern time, when Warner, Kaine and Scott, an African-American who is the dean of the state’s congressional delegation, issued their statement.

“Governor Northam has served the people of the Commonwealth faithfully for many years, but the events of the past 24 hours have inflicted immense pain and irrevocably broken the trust Virginians must have in their leaders,” said the three lawmakers, who initially resisted calling on the governor to quit. “He should step down and allow the Commonwealth to begin healing.”

Northam, standing next to his wife Pam at the news conference, spoke earnestly and was seemingly impervious to the wave of condemnation that the photograph had spawned. He appeared determine to maintain his innocence and said he would use the controversy as something of a teachable moment in the state where slaves first arrived 400 years ago.

Speaking to reporters for more than 40 minutes as a handful of protesters gathered outside the state Capitol demanding that he resign, the 59-year-old governor said he wanted to have “an honest conversation about racial justice.”

He called the image of two men “offensive, racist and despicable.” But he said, “I cannot in good conscience choose the path that would be easier, for me to duck my responsibility to reconcile.”

Northam, who was elected in 2017, asked Virginians for forgiveness and said he understood that not all of the state’s citizens would believe him.

While he was insistent that it was not him in the image from the 1984 Eastern Virginia Medical School yearbook, he appeared less assertive about other questions regarding his history. Asked why he was referred to as “coonman” on his yearbook page at the Virginia Military Institute, Northam said that two cadets a year older than him had given him the nickname but insisted that he did not know “their motives or intent.”

Further, his efforts to present himself as a healer were complicated by his discussions of the Michael Jackson-themed dance party and the matter of whether he could still perform Jackson’s “moonwalk” dance steps.

Northam was calm as he took questions, but was plainly bothered by the suggestion that he was bigoted or dishonest. A native of Virginia’s rural Eastern Shore, the governor noted that he went to integrated public schools in the 1970s, a time when many affluent white children fled to segregation academies, and he called himself “a man of honor,” invoking his leadership on VMI’s honor court.

“That is the most meaningful thing to me in my life,” Northam said. “I tell the truth. I’m telling the truth today.”

He said that he had a chance to sit down Friday night and look at the photo closely, and that classmates had told him there were photo mix-ups on other pages in the yearbook. He said he had not bought a copy of the yearbook and had never previously seen it.

But now that he has lost support from nearly all his allies in the state Capitol — both the House and Senate Democratic caucuses have urged him to quit — it is not clear how long Northam can last.

He will have a difficult time recruiting businesses to the state and could also face challenges raising campaign contributions, which is crucial given that all 140 seats of the state Legislature are on the ballot this fall and Democrats need to win only a handful of races to take control of both chambers.

Further, Northam is confronting a national party that will not ease up on him.

Democrats in the Trump era have adopted a sort of zero-tolerance approach in their ranks toward misconduct involving race and gender. With Republicans eager to level accusations of hypocrisy, Democratic leaders in Washington have sought to aggressively police the sort of misdeeds they have linked to Trump. They have pushed out lawmakers such as former Sen. Al Franken of Minnesota and former Rep. Ruben Kihuen of Nevada, both of whom were accused of sexual harassment.

With the 2020 Democratic presidential primary race getting underway, the pressure on Northam has been intense: The party’s White House hopefuls were some of the first officials to call on him to resign Friday night, beginning a cascade of demands that extended through the day Saturday.

Calls for Northam’s resignation also came from state Democrats like former Gov. Terry McAuliffe and Mayor Levar Stoney of Richmond, both longtime allies of the governor. By the end of the day, Northam had few public allies left beyond his own staff and some longtime friends, like the Rev. Kelvin Jones, an African-American whose Baptist church Northam attends when he is on the Eastern Shore.

“We cannot destroy somebody’s life for a choice we perceive they made,” said Jones, who traveled to Richmond on Saturday to be with the governor and said he did not think it was Northam in the picture.

The Virginia Constitution allows the impeachments of governors for “offending against the Commonwealth by malfeasance in office, corruption, neglect of duty or other high crime or misdemeanor.” If Northam chooses to remain in office and legislators seek his impeachment, the House of Delegates would be the first legislative chamber to consider the matter. The Senate would conduct any subsequent trial and determine whether Northam kept power.

The governor’s overnight political implosion began when the conservative website Big League Politics published a photograph from the yearbook Friday. The governor, in issuing his apology, admitted that he was in the photo but did not say which costume he had worn and offered his “absolute commitment to living up to the expectations Virginians set for me when they elected me to be their governor.”

Patrick Howley, editor-in-chief of Big League Politics, a website founded by former employees of Breitbart News, said Saturday on the NPR program “All Things Considered” that a “citizen whistleblower” had sent the image of the yearbook page to the publication. Howley declined to say how he had verified that Northam was in fact in the photo, other than to say he “checked it out.”

A low-key pediatric neurologist who entered politics only when he was elected to the state Senate in 2007, Northam was able to push through Medicaid expansion last year with bipartisan support. And late last year, he announced one of the most significant economic development achievements in recent Virginia history when Amazon announced it was adding a new headquarters in Arlington.

Northam was at the center of a separate political firestorm even before the yearbook photograph surfaced Friday, when he became embroiled in a renewed debate over abortion rights. Republicans seized on comments he made in an interview about a proposal concerning late-term abortions, suggesting Northam had effectively come out for infanticide. The governor and his allies sharply disputed those assertions.

Trump weighed in on both matters with a Twitter message Saturday calling Northam’s reversal on the yearbook photo and his recent remarks about abortion “unforgivable.”

The yearbook photo controversy was the latest agony over race to befall Virginia, which continues to struggle to move beyond its history of slavery and its 20th-century embrace of segregation.

Outside the mansion, where statues commemorating segregationists and civil rights heroes alike stand near the Jefferson-designed Capitol, some onlookers said they had come simply out of curiosity.

“What does that say about us?” said Michael Farrell, a Richmond physician who said he donated to Northam’s campaign. “It’s disturbing. It’s not that long ago.”