CHICAGO — Rasha Alhnaity arrived here earlier this month at a regional gathering of federal law enforcement applicants with some of the most-prized credentials of any of the nearly 150 candidates all pursuing the same thing: a place in the ranks of the U.S. Secret Service.

The 34-year-old data analyst holds masters' degrees in both business and health care administration. She is fluent in Arabic, and if there are any questions about her physical conditioning, agency officials need only scan the YouTube catalog of international martial arts events where she has competed as a fourth-degree black belt.

"I've been doing my homework,'' she said, anxiously waiting for the verdict after a first round of interviews. "I've worked very hard to pursue this life.''

Yet for every candidate approaching Alhnaity's clearly impressive qualifications, thousands of others seeking positions as agents and uniformed officers have been washing out of the Secret Service's most ambitious recruiting campaign in more than a decade during a period when the agency has faced unprecedented demands as it tries to emerge from controversies that have dogged it in recent years.

Complicating the agency's effort to boost its ranks, officials said, are otherwise promising candidates whose abuse of the amphetamine Adderall, or other prescription drugs, or their lack of candor about using them result in an abrupt removal from the process.

The problematic prescription drug histories, officials said, are emerging with troubling frequency in the midst of the hiring blitz aimed at rejuvenating an agency shadowed by a series of security breaches and recurring agent misconduct. Just two years ago, those controversies helped topple the service's first woman director, Julia Pierson.

An ongoing effort to add more than a 1,000 agents and uniformed officers to the ranks by next fall also comes during the most taxing 12-month period in the history of the service.

Beginning with the massive security operation that accompanied Pope Francis’ visit to the U.S. last fall and culminating with raucous primaries, summer political conventions and the general election campaign, agents and officers have been thrust into the most volatile political environment in recent history. While hundreds of agents have been crisscrossing the country with the candidates, vetting a record 3 million people at the conventions and rallies, others have been culling through tens of thousands of applicants, who are being eyed to provide relief to weary security details even as the giant inauguration security operation looms.

The succession of major security events has been so demanding that some of the most veteran agents maxed out their overtime allowances in June and have essentially been working for free since, said Maryland Rep. Elijah Cummings, the ranking Democrat on the House Oversight and Government Reform Committee, which has closely examined the agency's operations in the past two years.

The unrelenting pace is what has troubled both critics and advocates of the agency, who believe the grinding nature of the Secret Service's mission has largely contributed to its recent troubles. Consequently, they say, an infusion of personnel for both the uniformed officers who guard the White House and plain-clothes agents who protect its occupants and a host of other government officials and visiting dignitaries, is urgently needed.

"The Secret Service is stretched to and, in many cases, beyond its limits,'' a special investigative panel concluded in a review following Pierson's resignation. "Perhaps the service's greatest strength — the commitment of its personnel to sacrifice and do the job no matter what — has had unintended consequences.''

Secret Service Director Joseph Clancy, a career agent summoned from retirement by President Obama to help right the agency, said the finding continues to influence virtually every facet of an ongoing internal restructuring effort.

"Everything starts with that staffing piece,'' Clancy said in an interview with USA TODAY. "The panel was exactly right when they said we wear this (heavy workload) as a badge of honor, and we shouldn't. ... We don't want to be in that position. Our goal is to try to take that pressure off. We're never going to be able to remove all of that pressure, but we're working to remove some of that pressure.''