In the final weeks of a heated race to determine who will be Loudoun County’s top law enforcement officer, questions of character — not policing — are dominating the contest.

Four-term incumbent Stephen O. Simpson (I) has fielded criticism over campaign donations and his involvement in a private beverage company, while Mike Chapman (R) and Ron Speakman (I) have exchanged barbs over each other’s professional experience and personal integrity.

The sheriff’s race has become the most expensive of Loudoun’s local races this year, with Speakman spending about $112,000 — including about $108,000 in personal loans — so far. Simpson has spent nearly $105,000, and Chapman has spent about $42,000, according to campaign finance records.

Speakman, a former Leesburg police officer, drew the ire of Loudoun Republicans when he re­entered the race as an independent after losing the party’s nomination to Chapman in July. Speakman has run ads targeting Chapman, a former Drug Enforcement Administration agent, claiming that his “deceptive” résumélisted expertise and specific job titles he never held.

The Loudoun County Republican Committee launched a counteroffensive at a September news conference on the county courthouse steps, where Chapman addressed Speakman’s ads directly.

“They’ve been total distortions,” Chapman said, noting that his campaign “verified not only what I did but the level of expertise that I brought to those offices.”

At the courthouse, Loudoun Treasurer H. Roger Zurn Jr. (R) summarized the contents of a Fairfax County court file detailing Speakman’s affair with a woman who accused him of abuse and shot him in 1993.

“These are not qualifications for a Loudoun County Sheriff,” Zurn said. “Not close, nowhere near, unprecedented.”

Marti Miller, who dated Speakman, accused him of abuse during their relationship, which began when Speakman was a married father of two, according to court records. In interviews with The Washington Post, Speakman denied that he abused Miller, taking responsibility for the “bad decision” to initiate the affair but emphasizing that he was the victim in the shooting. Miller was convicted of unlawful wounding in the incident.

Speakman has also come under fire after he acknowledged that he messaged a lewd photograph to a woman’s cell phone. Speakman said the photo was intended as a joke, adding in a statement: “I obviously misjudged a person of my recent acquaintance and I regret that my hasty action caused her any discomfort.”

Simpson, who was generally spared in the crossfire between Speakman and Chapman, drew attention at a public forum Oct. 16 when he said his campaign was investigated by the FBI in connection with donations he received from Ashburn restaurateur Osama El-Atari. The businessman was sentenced to 12 years in federal prison in August 2010 for fraudulently obtaining more than $71 million in bank loans. Simpson said federal authorities also investigated allegations of impropriety in his dual role as sheriff and as president and chief executive of Performance Beverage Group, which distributes a sports beverage called Nine Iron.

Simpson’s attorney, William Coffield, said his client was cleared of wrongdoing in both inquiries by the U.S. attorney’s office.

FBI agents have questioned Simpson’s associates over several months about the sheriff’s role with Performance Beverage and his ties to a local businessman who paid for Simpson’s $51,750 investment in the company, according to sources who spoke on the condition of anonymity because they feared reprisals from the sheriff.

Simpson’s political opponents have seized upon his role with the beverage business, calling him a “part-time sheriff.”

Simpson has denied that accusation, noting that the job requires him to be on call 24 hours a day.

But law enforcement sources noted that Simpson took a leave of absence to work on the beverage business and missed the sheriff’s office’s annual budget presentation to the Board of Supervisors in March. Law enforcement sources and Simons Chase, former chief executive of Performance Beverage, said Simpson used the time to market Nine Iron at out-of-state golf tournaments, including the Honda Classic in Palm Beach Gardens, Fla.

Simpson, who declined to comment on the missed budget presentation, has said the focus on Performance Beverage is “a vendetta” to damage him politically, driven largely by a lawsuit filed against him in Alexandria Circuit Court in September by Chase, who is seeking $2.1 million in damages. In the complaint, Chase claims that Simpson engaged in fraud by selling the company’s product and collecting payments for himself and that Simpson misrepresented himself as the company CEO in the course of business.

Simpson said the timing of the complaint was politically motivated, referring to a December 2010 e-mail in which Chase noted that his lawsuit would be filed “when the time is right.”

Chase, who lives in California, said he does not have a stake in Loudoun politics.

“I’m not a resident of Loudoun County, and I don’t care what happens with the elections,” he said. “This is about a business dispute. Let’s let the jury decide.”

This story has been updated.