Philadelphia District Attorney Larry Krasner is pitching his reelection campaign as a fight for criminal justice reform — and against a return to injustices of the past.

“Do you want the future, where we are going to continue to keep those kinds of promises?” Krasner, 60, asked voters during a candidate forum last month, citing his reform-based 2017 campaign. “Or do you want the past?”

Carlos Vega, his challenger in the Democratic primary, is offering voters a hybrid: A reform-minded, experienced homicide prosecutor who says Krasner is making the city “vulnerable and unsafe.”

“We need a more responsible approach to criminal justice reform, as well as prosecuting violent criminals,” Vega, 64, told the same Philadelphia Bar Association forum. “Four years ago, we were promised that, through justice, we’d have a safer city. Philadelphia is more dangerous now than it’s been in the last three decades.”

The primary is a clash of personalities and prosecutorial philosophies.

Vega and Krasner have faced each other before, but in courtrooms. Krasner was a longtime defense and civil rights lawyer with no previous prosecutorial experience. And Vega, a 35-year prosecutor, was among a wave of firings by Krasner when he first took office.

The race is entering its final month before the May 18 primary amidst a historic spike in homicides and gun violence. Krasner’s reelection campaign is a key test for the reform movement that four years ago helped make him one of the most liberal big-city prosecutors in the country. And it comes as Krasner’s critics are increasingly pointing the finger at him for the violence plaguing the city.

An Inquirer analysis last month found that although arrests for illegal gun possession have nearly tripled during Krasner’s time in office, conviction rates have fallen from 63% to 49%.

» READ MORE: Philly gun arrests are on a record pace, but convictions drop under DA Krasner

Krasner says that police are presenting weaker cases to his office and that judges toss out charges when witnesses don’t appear in court. More broadly, he blames the coronavirus for an epidemic of mostly young men killing other young men, noting that violent crime has spiked in cities across the country during the pandemic.

“The best answer I have after talking to a whole lot of cops and criminologists and doing a lot of researching is: Look at what we lost in the pandemic,” Krasner said at another candidate forum last month.

“We lost high school classrooms that were open,” he said. “We lost rec centers. We lost swimming pools. We lost organized sports, both in and out of school, which I have never, ever, ever seen in my lifetime. We lost every after-school program.”

Vega says Krasner is just shifting the blame.

“Larry’s failure to prosecute gun crimes has directly contributed to the uptick in violence in our streets,” Vega said. “Instead of blaming others and making excuses, Larry should just do his job. We shouldn’t have to choose between reform and safety.”

The divide between them has played out in the city’s Laborers District Council, a politically powerful union group headed by Ryan Boyer. Its political action committee gave Krasner $12,600 this year, the maximum allowed, but also gave Vega $7,500.

Boyer said one local in his union backs Vega while another supports Krasner. But everyone is concerned about violent crime.

“With this level of violence, someone has to be held accountable,” Boyer said. “I don’t think we can run a modern city with this level of violence. It scares away investment. It scares away tourists.”

Democrat-turned-Republican Chuck Peruto, a defense lawyer who supported Krasner four years ago but now is one of his harshest critics, is running unopposed in the GOP primary.

» READ MORE: Philly’s Democratic Party rebuffs DA Larry Krasner’s bid for an endorsement

Krasner is touting his conviction integrity unit in campaign stops, noting it has secured the exoneration of 19 people convicted by his predecessors. His campaign literature includes a testimonial from one of them, Chester Hollman, saying, “It wasn’t until Larry Krasner became the DA that someone finally heard my voice and restored my liberty.” That’s a significant culture shift for an office with a history of tough-on-crime rhetoric.

Krasner has pointed to Vega’s attempt to keep in prison Anthony Wright, convicted of rape and murder in 1991 and found not guilty in a second trial in 2016. Wright was cleared by DNA evidence.

Vega said he was brought in to help in the 2016 retrial and was later deposed in a civil lawsuit that prompted the city to pay Wright almost $10 million. Vega noted he was not named as a defendant in that suit and accused Krasner of a “bald-face lie” in blaming him for the case.

“I was brought in at the eleventh hour, two weeks before the trial, just to question three witnesses,” Vega said.

Mustafa Rashed, a political consultant not working for either campaign, said Krasner can’t just run as a reformer this time.

“If the goal was public safety and criminal justice reform, those have to be married,” Rashed said.

Vega’s challenge, Rashed said, is finding a “middle lane” in a race that sometimes feels like Krasner versus the Fraternal Order of Police, the police union that has been harshly critical of Krasner.

Krasner has clashed at times with other criminal justice figures, from former U.S. Attorney William M. McSwain to Pennsylvania Attorney General Josh Shapiro. His relationship with the FOP is one of constant rhetorical warfare.

And he’s no darling in his own party. The Democratic City Committee voted this month for an “open primary,” denying Krasner an endorsement — a highly unusual step in a city where incumbents typically get the party nod. Party chair Bob Brady said some ward leaders driving the decision were unhappy with Krasner’s explanation for the surge in homicides and gun crimes.

It remains to be seen whether or how much that will hurt Krasner’s prospects. He’s running in an off-election year that typically lacks huge voter interest. And Krasner still has the backing of powerful progressive groups such as Reclaim Philadelphia. Krasner won the seven-candidate 2017 primary with 38% of the vote. But four out of five Democratic voters didn’t cast a ballot.

“Does Vega have the ability to make people pay attention so he can make his argument?” Rashed asked. “There’s clearly election fatigue, coming off a presidential year.”

Vega has polished and perfected an endearing stump speech that recounts him working the cash register of his mother’s New York bodega and climbing the prosecutorial ranks while working night shifts at UPS as a single father.

But whether he will have the necessary resources to unseat an incumbent still popular with many progressives is an open question. So is whether outside political groups, which played a big role in Krasner’s 2017 win, once again spend big.

Vega is competitive in campaign contributions, raising just more than $335,000 this year, with $355,000 in the bank as of March 29. Krasner raised more than $421,000 this year, with $351,000 in the bank.

Krasner benefited four years ago from almost $1.7 million spent by Philadelphia Justice & Public Safety, a PAC funded by George Soros, a billionaire philanthropist. A spokesperson for that PAC did not respond when asked whether it would again back Krasner.

Protect Our Police PAC, founded last year by retired Philadelphia police officers opposed to Krasner and progressive candidates backed by Soros, has said it will not endorse Vega, but intends to focus on defeating Krasner.

“This really is a contest between the past and the future,” Krasner said last week.