Republican members of Congress are focusing on the role of the Secret Service, as their frustration and anger grow over the agency's response to an attempt to assassinate presidential nominee Donald Trump.
A House committee hearing will on Monday grill its Director, Kimberly Cheatle -something Speaker Mike Johnson said would make for "must-see TV" for Americans concerned about security lapses at a Pennsylvania rally earlier this month.
"She's got a lot to answer for. And these concerns are bipartisan," Mr Johnson told CNN.
Ms Cheatle's agency is charged with providing protection to the president and his family, former presidents, those in line to the White House and other political candidates.
Republicans, who control the House, have been unified in pushing for Ms Cheatle to step down - or be fired - after a 20-year-old gunman was able to shoot the former president in the ear at the 13 July rally.
Committee Chairman James Comer is expected to describe the incident as "preventable" and the Secret Service as "the face of incompetence" in his opening remarks at the hearing.
"It is my firm belief, Director Cheatle, that you should resign," he will also say.
"However - in complete defiance - Director Cheatle has maintained she will not tender her resignation.
"Therefore, she will answer questions today from members of this committee seeking to provide clarity to the American people about how these events were allowed to transpire."
"Under Director Cheatle’s leadership, we question whether anyone is safe," Mr Comer will add.
"Not President Biden, not the First Lady, not the White House, not presidential candidates."
Ms Cheatle, meanwhile, is expected to say that she takes full responsibility for any security lapse.
“We must learn what happened and I will move heaven and earth to ensure an incident like 13 July does not happen again," she will tell the committee.
"Thinking about what we should have done differently is never far from my thoughts.”
Many of the lawmakers confronted Ms Cheatle at the Republican convention last week, releasing videos of them demanding answers.
In a new interview with Fox News, Trump said nobody warned him of a problem in the lead-up to the incident at the rally.
"Nobody mentioned it, nobody said there was a problem. I would've waited for 15, they could've said let's wait for 15 minutes, 20 minutes, five minutes, something," he said in the joint interview with his vice-presidential candidate JD Vance, which is due to air in full on Monday.
"How did somebody get on the roof and why wasn't he reported? Because people saw that he was on the roof."
US media is reporting that Trump sought additional security in the months leading up to the assassination attempt, but that the agency had turned them down or been unable to fulfil the requests due to staffing shortages. CBS News, BBC's news partner, has reported that the former president's security frustrations go back two years.
Agency spokesperson Anthony Guglielmi said in a statement that "in some instances where specific Secret Service specialised units or resources were not provided, the agency made modifications". That included relying on state and local law enforcement.
Eric Trump, the former president's son, said he had been calling for beefed-up security throughout the campaign, as he blamed the Biden administration and Ms Cheatle on Sunday for the assassination attempt and argued there had been "no accountability" for the agency's actions.
"She should be out of a job," he told Fox News.
Speaking to CNN, Mr Johnson said that in addition to the House hearing, lawmakers on Monday would release more details about a bipartisan task force with subpoena authority charged with investigating the Secret Service's response.
"The initial excuses that [Ms Cheatle] has given for the lapses that happened last Saturday are just unbelievable, so we're going to get down to the bottom of it," he said.
Senators, too, are preparing to dig in on the Secret Service.
Republican Senator Ron Johnson told Fox News on Sunday that he would soon release "preliminary" information from his own report investigating the attack.
That report is intended to encourage people to come forward with more footage and first-hand accounts. He added that his investigation was now bipartisan, and would be conducted with Senator Richard Blumenthal, a Democrat from Connecticut.
The Department of Homeland Security's inspector general is also looking at the attack, which occurred after the Secret Service identified the gunman as suspicious some 20 minutes before he opened fire, lawmakers revealed this weekend.
Mr Johnson's appearance on CNN came just a day after reports emerged that top officials at the Secret Service had denied some requests from Trump's security team for additional resources in the two years leading up to the assassination attempt.
The report, first published in the Washington Post, external, said the agency had refused additional resources such as more agents and snipers because of a lack of resources and staffing shortages within the Secret Service.
Mr Johnson blamed the Department of Homeland Security (DHS) for failing to allocate more resources to the Secret Service, an agency that it oversees.
The Republican House speaker told CNN on Sunday that Congress had increased funding to DHS in recent years, but that DHS Secretary Alejandro Mayorkas was responsible for ensuring the Secret Service had enough funds.
"Secretary Mayorkas is in charge of that agency. If he needed to allocate more resources to the Secret Service then that should have been done," Mr Johnson said.
Mr Johnson added that he had spoken to Mr Mayorkas hours after the assassination attempt and that the DHS leader was unable to answer "basic questions", including whether the gunman, Thomas Crooks, had used a drone to survey the outdoor rally area.
Law enforcement officials told US media on Saturday that Crooks had flown a drone above the site ahead of the shooting.
Trump has made several appearances since the incident, including at a rally in Grand Rapids, Michigan on Saturday, where he told the crowd that he "took a bullet for Democracy".
His former White House physician, Dr Ronny Jackson, released a statement the same day saying the bullet created a 2cm-wide wound on Trump's ear that was beginning to "heal properly".
