Virginia Governor Ralph Northam is not resigning, his communications director, Ofirah Yheskel, told CBS News on Saturday, as he faced mounting pressure to step down over a racist yearbook photo.

Northam's page in the 1984 East Virginia Medical School yearbook contains a photograph of two people — one appearing to be wearing blackface and another in a Ku Klux Klan costume. He said Friday night he is pictured in the photo.

However, he changed his story in a press conference Friday. "I believe then and now that I am not either of the people in the photo," Northam said.

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He acknowledged that the photo was "disgusting," "racist," and 'offensive." But he claimed that when he was shown the yearbook Friday, he was seeing it for the first time. "I was unaware of what was on my page," he said.

CBS News also uncovered a page on Friday from Northam's yearbook at the Virginia Military Institute that had nicknames listed underneath his name. One of them was "Coonman," a racial slur.

Lt. Gov. Justin Fairfax, who is the second African-American to serve in statewide office in Virginia history, offered a response Saturday, although he did not call for Northam to resign outright.

"The Governor needed to apologize, and I am glad that he did so. He also reached out to me personally to express his sincere regrets and to apologize," Fairfax said, adding that he had worked closely with the governor and considered him a friend.

"While his career has been marked by service to children, soldiers, and constituents, I cannot condone the actions from his past that, at the very least, suggest a comfort with Virginia's darker history of white supremacy, racial stereotyping, and intimidation," Fairfax said. "At this critical and defining moment in the history of Virginia and this nation, we need leaders with the ability to unite and help us rise to the better angels of our nature."

On Saturday night, President Trump posted two tweets about Northam. In the first, Mr. Trump wrote that Northam said he was not one of the people in the photo "24 hours after apologizing for appearing in the picture and after making the most horrible statement on "super" late term abortion. Unforgivable!"

In the second tweet, Mr. Trump said Northam's Republican challenger Ed Gillespie "must now be thinking Malpractice and Dereliction of Duty with regard to his Opposition Research Staff. If they find that terrible picture before the election, he wins by 20 points!"

Democrat Governor Ralph Northam of Virginia just stated, “I believe that I am not either of the people in that photo.” This was 24 hours after apologizing for appearing in the picture and after making the most horrible statement on “super” late term abortion. Unforgivable! — Donald J. Trump (@realDonaldTrump) February 3, 2019

Ed Gillespie, who ran for Governor of the Great State of Virginia against Ralph Northam, must now be thinking Malpractice and Dereliction of Duty with regard to his Opposition Research Staff. If they find that terrible picture before the election, he wins by 20 points! — Donald J. Trump (@realDonaldTrump) February 3, 2019

Virginia Attorney General Mark Herring went a step further and called on Northam to step down, saying that Fairfax would have his "complete support and commitment to ensuring his success" if Fairfax became governor.

On Saturday evening, Sens. Tim Kaine and Mark Warner -- two former governors -- along with Rep. Bobby Scott released a joint statement calling on Northam to resign.

"After we watched his press conference today, we called Governor Northam to tell him that we no longer believe he can effectively serve as Governor of Virginia and that he must resign. 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. He should step down and allow the Commonwealth to begin healing," the statement said.

Northam faced immediate backlash Friday night, with many political figures on both sides of the aisle calling for him to resign.

"Gov. Northam should resign, this type of character flaw is unacceptable for any elected official seeking the support of the Black vote," Derrick Johnson, the president and CEO of the NAACP, said in a statement. "It's sad but eerily prophetic this revelation came during Black History Month; but while we uplift the current and historical achievements of African Americans, we must also acknowledge the extent to which racism is a part of our history in America."

Other prominent black political figures called on Northam to resign Friday night, including Congressional Black Caucus Chairwoman Karen Bass and House Democratic Caucus Chairman Hakeem Jeffries.

"Ralph Northam served in our nation's military, treated thousands of families as a medical doctor, and had the audacity to ask for Black votes when he wanted to become governor, yet never once mentioned that he thought it was ok to be in black face or dressed as a Klansman," Bass said in a statement. "An apology now isn't enough. The governor needs to learn that it's not about what you do once you're caught. Instead, it's about the things you do when you think no one is watching."

Ralph Northam yearbook page WTKR-3 Brendan Ponton

Several Democratic presidential candidates urged Northam to step down, including Senators Kamala Harris, Cory Booker and Kirsten Gillibrand, as well as Julián Castro and John Delaney.

Terry McAuliffe, a Democrat who served as Virginia governor before Northam, shared that belief.

"Ralph Northam is my friend and he served well as my Lt. Governor and as Governor. His actions on display in this photo were racist, unacceptable and inexcusable at any age and any time," McAuliffe said. "The situation that he has put himself and the Commonwealth of Virginia in is untenable. It's time for Ralph to step down, and for the Commonwealth to move forward."

Virginia state House Democrats also released a statement Friday night calling on Northam to resign, saying "it brings us no pleasure to do so." Virginia state Senate Democrats did the same.

Mayor Levar Stoney of Richmond and three Democratic members of Virginia's congressional delegation, Reps. Donald McEachin, Abigail Spanberger and Elaine Luria, also urged Northam to step down.

Republicans also urged Northam to resign. Virginia GOP Chair Jack Wilson called for Northam's resignation almost immediately after the yearbook page surfaced. Republican Governors Association Chairman Governor Pete Ricketts said in a statement later on Friday that Northam had "failed Virginia," and needed to step down.

The calls extended beyond the state.

"I don't see the governor's got any other choice other than to step aside," Democratic New Jersey Gov. Phil Murphy, the vice chair of the Democratic Governors Association who is set to take over in 2020, said Friday night on MSNBC. Former Vice President Joe Biden tweeted that Northam should resign on Saturday.

A protest was held outside the Virginia Governor's Mansion on Saturday morning in Richmond, the capital of Virginia. Protesters held signs and chanted slogans such as "New Virginia Way" and "Resign Now."

"We made the decision to let Governor Northam do the correct thing and resign this morning — we have gotten word he will not do so this morning," said a statement by the Virginia Democratic Party released Saturday.

Northam released a statement Friday afternoon apologizing: "I am deeply sorry for the decision I made to appear as I did in this photo and for the hurt that decision caused then and now."

However, he indicated he was not willing to step down as governor.

"This behavior is not in keeping with who I am today and the values I have fought for throughout my career in the military, in medicine, and in public service. But I want to be clear, I understand how this decision shakes Virginians' faith in that commitment," Northam said. "I recognize that it will take time and serious effort to heal the damage this conduct has caused. I am ready to do that important work. The first step is to offer my sincerest apology and to state my absolute commitment to living up to the expectations Virginians set for me when they elected me to be their Governor."

Several hours later Friday night, Northam tweeted a video saying his previous statement fell "far short of the standard you set for me when you elected me to be your governor" and "I believe you deserve to hear directly from me."

"That photo, and the racist and offensive attitudes it represents, does not reflect the person I am today, or the way that I have conducted myself as a soldier, a doctor, and a public servant," Northam said. "I am deeply sorry. I cannot change the decisions I made, nor can I undo the harm my behavior caused then and today. But I accept responsibility for my past actions, and I am ready to do the hard work of regaining your trust."

Northam spent Saturday morning phoning back many of the fellow Democrats he'd reached out to on Friday, according to two party operatives familiar with the conversations. In the hours after the photo first surfaced, Northam did not recall being in the photo, said the operatives, who were granted anonymity to speak frankly about private conversations.

The governor proceeded with his written and video statements, where he apologized for "racist" behavior but made no mention of stepping down.

In the hours after the release of the statements, however, Northam's stance began to shift after he heard from classmates who told him he wasn't one of the two people in the photo. By Saturday morning, the governor appeared to agree with those recollections and began phoning back senior Virginia Democrats at the federal and state level to say he wouldn't be stepping down.

Ed O'Keefe contributed to this report.