In an upset brought about by local scandal, demographic evolution and personal chutzpah, Lupe Valdez, the daughter of a Mexican immigrant farm worker, became the first ever Democrat and woman to head the county's sole law enforcement office, which includes Texas' second largest city.
"Since I won, every time I go to a Democratic meeting, they go crazy," Ms Valdez, 57, told the New York Times.
Despite the fact that she had little in the way of money and a campaign led by novices, Ms Valdez won comfortably.
"We fought like we were losing," said Ms Valdez, a former prison guard, who had no idea how she was faring until the votes were counted because she could not afford the $12,000 (£6,500) for a poll. Her Republican rival, Danny Chandler, is a 29-year veteran of the department who hired a PR company to guide his campaign. But the Republicans were dogged by controversy from the outset.
The current sheriff, Jim Bowles, who held the post for 20 years was indicted on charges of taking more than $100,000 (£54,000) from vendors seeking contracts. He lost the Republican primary to Mr Chandler but continued publicly to attack him.
In the closing days of the campaign Mr Chandler tried to attack Ms Valdez over her sexual orientation, claiming Gay and Lesbian Victory Fund's endorsement of her candidacy committed her to promoting a gay agenda.
"It just simply is not relevant," Ms Valdez told the Fort Worth Star-Telegram before the election. "Desperate people do desperate things, and I think they're reaching."
Her win was aided by a mixture of white flight from the area and a steady increase in the black and Hispanic population, which is heavily Democratic. A Republican state district court judge who had sat on the bench for 15 years also lost to a woman in a surprise defeat.
"The Democrats are on their way back," Cal Jillson, a political science professor at Southern Methodist University told the Dallas Morning News. "We can now call Dallas County a two-party, competitive county, which it has not been for 15 or more years."
It was also one of a handful of victories for openly lesbian and gay candidates across the country, with the conservative bastions of Idaho and North Carolina getting their first openly lesbian and gay state officials.
In Dallas the sheriff's department is struggling to adjust to their new boss.
Ms Valdez will take over a $130,300 a year job in charge of 7,000 prisoners and 1,322 deputies, detention officers and bailiffs.
"Right now the department is in a little bit of shock," said Lt Mark Howard, chair of the Sheriff's Association executive board. "We're just hoping she'll do what she promised. It would do no good to sabotage her. We want her to succeedd."
"It's up to her to earn our trust," said David Teel, second vice-president of the Sheriff's Department chapter of the Fraternal Order of Police. "The ball's in her court. She's got a long, hard road ahead."
Ms Valdez is undaunted. "Excuse me," she said. "Going from migrant worker to a professional, that was a challenge. Going from jailer to federal agent, that was a challenge." Compared to all that, she says, this new job is "not a challenge".