The head of Fairfax County’s busy elections office is stepping down after four years of low employee morale and external criticism of a department that manages registration and ballots for an electorate of 700,000 voters.

Cameron Quinn, whose four-year term expires Wednesday, submitted a letter to the county’s Electoral Board on Monday evening asking that she not be reappointed.

Quinn, who took over Virginia’s busiest elections office in 2011, cited health problems and the stress of overseeing an office that coordinates elections in 241 precincts — pressure that is bound to increase during the 2016 presidential elections.

“I have recognized that, given the health challenges that have manifested since I began this job, it is not prudent to intentionally go through such stress as is engendered by a presidential election year in this position under the current circumstances,” Quinn said in her letter.

In an interview Tuesday, Quinn said that her job has been frustrating at times but that she was able to make important strides.

Among them: upgrading the county’s voting machines and successfully executing closely monitored ballot recounts after last year’s contests between Sen. Mark R. Warner (D-Va.) and Republican Ed Gillespie and the 2013 race between Virginia Attorney General Mark R. Herring (D) and State Sen. Mark D. Obenshain (R).

“It is a very frustrating office with lots of challenges,” Quinn said. “It’s also got some very good people that generally do very good work.”

Quinn’s time as general registrar has been marked by sinking employee morale in an office that had five general registrars in the 10 years before she took over.

A 2013 consultant’s report commissioned by the county to investigate the instability found that Quinn’s management style exacerbated some problems.

The report found “considerable anger and confusion” among the agency’s 28 workers, leading to poor organization and bad customer service.

Quinn, a Republican who had been secretary of the state Board of Elections, faced some accusations of political favoritism inside the office, but the Electoral Board determined that the allegations were unfounded.

Similar claims surfaced in a 2012 Fairfax Circuit Court lawsuit, filed by the county’s Democratic Party, that accused Quinn and Electoral Board members of politically motivated restrictions that kept observers in polling stations from answering questions from voters that could help them understand their rights.

Both sides now agree that observers can talk to voters about anything short of instructing them how to vote.

Acting on the consultant’s report, the Electoral Board required Quinn to take a management-training course and hire a chief operating officer to oversee daily operations.

Katherine K. Hanley, the former chair of the County Board of Supervisors who is secretary of the Electoral Board, said she knew that Quinn’s resignation was forthcoming.

“It’s a tough job in a tough office, and we face tough challenges,” said Hanley, who is among the three-member board’s two Democrats.

Hanley said the Electoral Board has launched a nationwide search for a new general registrar with experience overseeing a complex elections office.