Jackson receiving 24 percent of the votes, which edged out L.A. City Attorney Carmen Trutanich by just 2 percent. Trutanich had been considered the favorite to become the county's top prosecutor.
Lacey pulled in 32 percent of the votes, but because she didn't receive a majority, she and Jackson will head to the general election. If Lacey wins there, she will become the county's first woman and black district attorney. She was the only one of the five prosecutors in the race who received retiring District Attorney Steve Cooley's endorsement.
"I'm very grateful to the voters, that they read up, that they listened, that they investigated our backgrounds, our experience," Lacey said.
This was the first district attorney election in 48 years without an incumbent running.
Jackson was quick to differentiate himself from Lacey on Wednesday morning.
"I think that's what the voters are going to have to decide. Who do they want to run this office? Do they want a modern prosecutor, or do they want an administrator? It comes down to that question," he said.
Both are courtroom veterans. Jackson has most recently been in the spotlight for his prosecution of cases like the Spector murder trial. Both Lacey and Jackson agree on the need for rehabilitation and changes because of the three-strikes law. Both see one of the biggest impacts on the justice system as the move of thousands of state prisoners to county jails.
Trutanich may have come in third in the race for district attorney, but he intends to run again for city attorney in the November election.
"I am looking forward to a second term right now," he said. "I love my job, I love working for the city."
Trutanich had more than $1.1 million to fund his campaign, the strongest name recognition of all the candidates and many big name endorsements, including from Gov. Jerry Brown and Los Angeles County Sheriff Lee Baca.
In the San Fernando Valley, voters will be choosing between two longtime Democratic incumbents in November.
In the 30th Congressional District, Brad Sherman received 42 percent of the vote. Howard Berman received 32 percent of the vote.
The vote is too close to determine if voters truly rejected Proposition 29. The vote was split 51 to 49 percent against the proposition.
The initiative would have imposed an additional $1-per-pack tax on cigarettes.
The extra tax money raised through the initiative would go to cancer research. Opponents argue it would hurt the economy by sending California tax money out of state.
California has a smoking rate of about 12 percent and hasn't raised taxes on tobacco since 2000.
Voters passed Proposition 28, which will limit lawmakers to 12 years in the state Legislature, but allow them to spend that time in one house or a combination in both houses.
Supporters say the measure will promote consistency and reduce the influence of lobbyists. Critics warned the change would lead to entrenchment in the state Capitol.