The Washington Post’s Jenna Johnson explains what the stakes are for Donald Trump’s presidential campaign following the release by The Post of a 2005 video in which he makes vulgar comments about women. (Bastien Inzaurralde/The Washington Post)

The Republican Party plunged into an epic and historic political crisis Saturday with just a month to go until Election Day as a growing wave of GOP lawmakers called on defiant presidential nominee Donald Trump to drop out of the race in the wake of a video showing him make crude sexual remarks.

The fallout from the tape published by The Washington Post — in which Trump bragged in obscene language about forcing himself on women sexually — threatens to endanger the party’s hold on both houses of Congress in addition to the White House, which many Republicans now fear is lost. The episode also comes ahead of Sunday’s second presidential debate in St. Louis, which was already a crucial moment but could determine how widely the damage spreads.

By midafternoon Saturday, more than two dozen Republican lawmakers had called on Trump to leave the race, often touting vice presidential candidate Mike Pence as an alternative. Others including Sen. John McCain (R-Ariz.), the 2008 GOP nominee, said they could no longer vote for Trump but stopped short of calling on him to drop out. Still, the Republican Party’s top leadership — including House Speaker Paul D. Ryan (Wis.), Senate Majority Leader Mitch McConnell (Ky.) and party chairman Reince Priebus — continued to support Trump even as they denounced his comments.

Trump, who offered a qualified apology for the remarks in an overnight video statement while also attacking former president Bill Clinton, told The Post he would not drop out under any circumstances.

“I’d never withdraw. I’ve never withdrawn in my life,” Trump said in a Saturday morning phone call from his home in Trump Tower in New York. “No, I’m not quitting this race. I have tremendous support.

“They’re not going to make me quit, and they can’t make me quit,” Trump added, speaking of those who have urged him to step aside. “The Republicans, you’ve got to remember, have been running for a long time. The reason they don’t win is because they don’t stick together.”

In the 2005 videotape, Trump boasted in vulgar language about kissing, groping and trying to have sex with women during a conversation caught on a hot microphone, saying that “when you’re a star, they let you do it. They let you do anything.”

Democratic presidential nominee Hillary Clinton and her allies seized on the video as another in a long line of disqualifying remarks and actions by Trump, and increased their pressure on Republican candidates to disavow their support of him or risk being tied to him on Election Day. Democrats are now openly confident they will win the Senate and increasingly optimistic that they could even flip control of the House, which seemed out of reach just a few days ago.

Clinton does not plan to do any interviews or make any further statement herself until the debate Sunday, when she plans to quickly address Trump’s fitness for office, said a close aide who spoke on the condition of anonymity to describe some of the internal discussions. Several Clinton associates said she will not detail the particulars of Trump’s comments, instead attempting to show her fitness for high office by contrast.

Another burst of offensive remarks by Trump emerged Saturday as CNN aired a review of hours of newly uncovered audio from shock-jock Howard Stern’s show. Trump spoke of his daughter Ivanka’s breasts, three-way sex and not dating women who are older than 35. He also described barging in on nude Miss Universe beauty pageant contestants in their dressing room, characterizing his visits as inspections.

Several Democrats said they think Trump will come into Sunday’s town-hall-style debate with the mind set of a “wounded animal,” a factor that could make him more dangerous to Clinton and to himself.

In the wake of a new Washington Post report showing Republican presidential nominee Donald Trump speaking in very lewd terms about women in 2005, some Republicans are calling for Trump to step down as nominee. (Thomas Johnson/The Washington Post)

“I’ve never seen a candidate walk into a debate with this much at stake,” said longtime Clinton ally James Carville. “He’s overweight, he’s old, he’s tired and he’s crabby. And he’s going to have a very long hour-and-a-half.”

Trump and his surrogates signaled that the nominee could defend himself by attacking Bill Clinton, whom Trump has accused of abusing women and making comments while golfing with Trump that are more crude than the ones Trump made in 2005. On Saturday night, Trump retweeted two messages from an account labeled as belonging to Juanita Broaddrick, who alleged in 1999 that Bill Clinton had raped her in April 1978. The tweets accused Bill Clinton of being a “rapist” and accused Hillary Clinton of threatening her; the Clintons have repeatedly denied the allegations.

Some news coverage of Trump included warnings of graphic material or profane language, another sign of how ugly the election has become and, given Trump’s threats to invoke Bill Clinton’s infidelities, how much worse it might get.

Roger Stone, a longtime Republican operative and outside Trump adviser, said Saturday that he and the InfoWars conspiracy website were selling 10,000 T-shirts with Bill Clinton’s face next to the word “rape,” a dark parody of President Obama’s 2008 “Hope” posters. He worried that Trump had missed a “prime opportunity” to attack Hillary Clinton over the affairs, but said there was still a way for Trump to litigate it.

“It’s not about adultery,” Stone said. “It’s about Bill hiring heavy-handed private detectives. It’s about violence against women. I know you and your colleagues want this to be about infidelity, but it’s about Hillary Clinton enabling attacks on women.”

A growing number of elected lawmakers and other prominent Republicans said they simply cannot vote for Trump, given the video. McCain, who is up for reelection in November, said Saturday that he and his wife would not vote for Trump and will instead “write in the name of some good conservative Republican who is qualified to be president.” McCain had supported Trump even though the businessman joked about him being captured during the Vietnam War and then refused to apologize.

Many said they would like to hand the ticket over to Pence, but experts said it would be almost impossible logistically for the party to replace its nominee a month from the election. Among those calling for Trump to drop out is the third-highest ranking Republican in the Senate, John Thune of South Dakota, who tweeted Saturday: “Donald Trump should withdraw and Mike Pence should be our nominee effective immediately.”

Condoleezza Rice, who was secretary of state during George W. Bush’s administration, posted on Facebook: “Enough! Donald Trump should not be President. He should withdraw. As a Republican, I hope to support someone who has the dignity and stature to run for the highest office in the greatest democracy on earth.”

The calls for Trump to step aside started Friday night, after several weeks of growing confidence among congressional Republicans that their candidates had distinguished themselves enough from Trump that they would maintain the majorities. But then they waited and waited for Trump to fully apologize for his comments, leading to a first wave of denunciations from those who had already said they wouldn’t vote for Trump or who had avoided taking a stance.

Sen. Mark Kirk (Ill.), who revoked his endorsement of Trump in June, called on Trump to drop out so that the party could “engage rules for emergency replacement.” Sen. Mike Lee (Utah), one of very few Republican senators who never endorsed Trump, called for the nominee to “step aside” and asked conservatives to find a new candidate.

“It’s occurred to me on countless occasions today that if anyone spoke to my wife, my daughter, my mother or any of my five sisters the way Mr. Trump has spoken to women, I wouldn’t hire that person. I wouldn’t hire that person, wouldn’t want to be associated with that person,” Lee said in a video filmed at his home in Utah. “And, I certainly don’t think I would feel comfortable hiring that person to be the leader of the free world.”

On Saturday morning, the calls increased and began to include some of Trump’s supporters and those from strongly Republican states.

“As disappointed as I’ve been with his antics throughout this campaign, I thought supporting the nominee was the best thing for our country and our party,” Rep. Martha Roby (Ala.) said in a statement. “Now, it is abundantly clear that the best thing for our country and for our party is for Trump to step aside and allow a responsible, respectable Republican to lead the ticket.”

Kelly Ayotte, the New Hampshire senator in a tight reelection race, who had said she supported but did not endorse Trump, tweeted Saturday morning that she would not vote for him and would instead write in Pence.

“I cannot and will not support a candidate for president who brags about degrading and assaulting women,” Ayotte said in a statement.

Some fundraisers for Trump worry that pledged donations might not come in during the final four weeks and that new donations might dry up. But GOP megadonors Robert and Rebekah Mercer, two of the most influential figures in Trump’s orbit, said Saturday that their support for the GOP nominee has not faltered: “We are completely indifferent to Mr. Trump’s locker room braggadocio.”

Trump was supposed to campaign Saturday in Wisconsin with Ryan, Priebus and other prominent Republicans, but Ryan rescinded the invitation on Friday. Pence was supposed to go in Trump’s place but decided against it to give Trump space to navigate the fallout from his statements, according to a campaign aide.

After avoiding questions about Trump’s comments at campaign events on Friday, Pence issued a statement on Saturday that said: “As a husband and father, I was offended by the words and actions described by Donald Trump in the eleven-year-old video released yesterday. I do not condone his remarks and cannot defend them. I am grateful that he has expressed remorse and apologized to the American people.”

Trump’s wife, Melania, released a similar statement: “The words my husband used are unacceptable and offensive to me. This does not represent the man that I know. He has the heart and mind of a leader. I hope people will accept his apology, as I have, and focus on the important issues facing our nation and the world.”

In both New Hampshire and Ohio, the GOP chairs signaled there would be no repercussions from the party for any elected officials or others who make a clean break from the nominee.

New Hampshire GOP chair Jennifer Horn issued a statement condemning Trump’s “erratic behavior” and “outrageous comments.” She added, “There will be no repercussions from the party directed at those who choose not to support Donald Trump.

In Ohio, party chair Matt Borges said in an interview that the state party would be “fully supportive” of Sen. Rob Portman, who is running for reelection against former governor Ted Strickland.

“Rob needs to know that we are fully supportive of his campaign,” Borges said in a phone interview. “However he chooses to proceed there will be no ramifications from the state party.”

Trump said in a statement that he planned to spend Saturday preparing for Sunday’s presidential debate with the help of New Jersey Gov. Chris Christie, Sen. Jeff Sessions (Ala.) and Priebus, who on Friday said that no one should ever talk about women the way that Trump did in 2005.

On Saturday morning, Trump broke an hours-long silence and tweeted: “Certainly has been an interesting 24 hours!” He tweeted again Saturday afternoon: “The media and establishment want me out of the race so badly - I WILL NEVER DROP OUT OF THE RACE, WILL NEVER LET MY SUPPORTERS DOWN!”

Meanwhile, Trump’s 2005 comments played again and again on cable news, upstaging even a dangerous hurricane. Some of Trump’s surrogates and prominent supporters came to his defense.

Sen. Roy Blunt (Mo.), a member of the party leadership who is facing a tough reelection battle, said Saturday that Trump’s comments were “absolutely unacceptable,” but he dismissed the idea that Trump could step aside 30 days before the election to make way for another nominee.

“I think that’s an unrealistic solution,” Blunt said. “The devastation of Obamacare, the out-of-control regulators, the foreign policy that our friends don’t trust us, make a third Obama term an unacceptable alternative.”

Asked whether he would vote for Trump, Blunt asked: “Didn’t I just say that?”

Dallas investor Doug Deason dismissed the episode as a manufactured media story.

“It’s just CNN and the press making a big deal out of nothing,” he said. “Anybody who is surprised about that or appalled or shocked is disingenuous. People knew that Trump was like that in those days. There’s probably more of it out there. He’s not like that anymore. He is a changed guy. We are a nation that believes in redemption and second chances, right? I don’t think he’s been that way for a very long time.”

Late Saturday afternoon, Trump emerged from Trump Tower with a swarm of U.S. Secret Service agents, surprising reporters who had staked out the lobby and delighting tourists and supporters hoping for a sighting.

As Trump waved at the crowd, reporters fired off questions: Will he stay in the race? What’s his message to his supporters? For the Republican Party?

“Tremendous support!” Trump said. “Tremendous support!”

When asked if he would stay in the race, Trump responded: “One hundred percent.”

Sullivan reported from New York. Abby Phillip in New York; Dan Balz, David Weigel and Jose A. DelReal in St. Louis; Matea Gold and Aaron Blake in Washington; and David Weigel in Mount Vernon, Mo., contributed to this report.