The Secret Service and its director, Kimberly Cheatle, remain under intense scrutiny after the assassination attempt on Donald Trump, with politicians across the spectrum questioning how a gunman could have got so close to the former president during a rally.

Ms Cheatle said in 2021 that the service “has a zero fail mission”, adding: “They have to come in every day prepared and ready with their game-face on.”

She is now facing calls to resign and will testify on Capitol Hill on Monday after Mr Trump suffered an injured ear when a gunman opened fire during a July 13 rally in Pennsylvania when he was supposed to be carefully guarded.

Ms Cheatle has already described the shooting as “unacceptable”, and when asked who bears the most responsibility, she said ultimately it is the Secret Service that protects the former president.

“The buck stops with me,” Ms Cheatle told ABC News. “I am the director of the Secret Service.”

Donald Trump was surrounded by Secret Service agents as he left the stage with a bloodied ear following the attempt on his life (Gene J Puskar/AP)

But she said she has no plans to resign, and so far she has the Biden administration’s backing.

President Joe Biden appointed Ms Cheatle in August 2022 to take over an agency with a history of scandals, and she worked to bolster diverse hiring, especially of women in the male-dominated service.

The second woman to lead the Secret Service, Ms Cheatle worked her way up for 27 years before leaving in 2021 for a job as a security executive at PepsiCo. Mr Biden brought her back.

Now, she faces her most serious challenge: figuring out what went wrong with the agency’s core responsibility to protect presidents and whether she can maintain the support – or the job itself – to make changes.

Details are still unfolding about signs of trouble on the day of the assassination attempt, including the steps taken by the Secret Service and local authorities to secure a building that the shooter, Thomas Matthew Crooks, climbed within 135 metres of where Mr Trump was speaking.

An ex-fire chief at the rally, Corey Comperatore, was killed and two others were injured.

The Biden administration has directed an independent review of security at the rally. The Homeland Security Department’s inspector general has opened three investigations and congressional committees have launched others as calls mount for Ms Cheatle to resign. Two Republican senators demanding answers followed her as she walked through the Republican National Convention this past week.

“The nation deserves answers and accountability,” Senate minority leader Mitch McConnell said on social media platform X. “New leadership at the Secret Service would be an important step in that direction.”

Donald Trump, surrounded by Secret Service agents, raised his fist as he left the stage following the assassination attempt (Evan Vucci/AP)

In the House, Speaker Mike Johnson said on X that Mr Biden should fire Ms Cheatle immediately, noting Mr Comperatore’s death and saying that “we… were millimetres away from losing President Trump. It is inexcusable”.

The House Oversight and Accountability Committee has subpoenaed Ms Cheatle to appear on Monday.

After the shooting, Ms Cheatle and the female Secret Service agents who protected Mr Trump have faced scathing criticism and questions about whether Ms Cheatle lowered hiring standards. Supporters are adamant that has not happened.

“It is disrespectful to the women of the Secret Service of the Department of Homeland Security and to women law enforcement officers around the nation to imply that their gender disqualifies them from service to the nation and their communities,” said Kristie Canegallo, Homeland Security’s acting deputy secretary.

Ms Canegallo said Ms Cheatle advocated for a law passed this year that authorised overtime pay for Secret Service agents and successfully oversaw nine high-profile events such as political conventions. The agency under her watch also protected Mr Biden during his trip to Ukraine without problems, she added.

Ms Cheatle applied for the Secret Service while she was still in college. She was told to wait until she had graduated and has previously said it ultimately took a little over two years to get hired: “I was pretty persistent.”

After training, she was assigned to the Detroit office where she spent just over four years. She then transferred to Washington where she served on the Treasury secretary’s detail and protected then vice-president Dick Cheney, including on 9/11.

Other positions during her time with the agency include special agent in charge of the Atlanta field office and special agent in charge of the agency’s training facility in Maryland.

She became the first woman to be named assistant director of protective operations, the division that provides protection to the president and other dignitaries.