By Matt Petrillo

PHILADELPHIA (CBS) — Ahead of the May primary, the race for Philadelphia district attorney is heating up. The race is a good example of how Philly politics can get rough and tumble.

In a rare move, Philadelphia’s Democratic Party is not endorsing any candidate for district attorney. That includes the incumbent, Larry Krasner.

“It is expected. It is exactly what they did last time,” Krasner said. “And last time, we won with more votes than any district attorney candidate in at least 20 years.”

Carlos Vega is a retired homicide prosecutor and Krasner’s opponent on the Democratic ticket.

“The fact that the Democratic Party is not endorsing an incumbent speaks volumes and is the report card that he has failed our community,” Vega said.

Another unusual element in the DA’s race is the city’s Fraternal Order of Police urging Republican officers to switch their party to become Democrats and vote for Vega in the May primary, all in an effort to take get the incumbent, Krasner, out of office.

The police union is not keeping tabs on how many have done so, but city officials say more than 3,300 voters have changed their registration to Democrats this year.

“Now you have fake Democrats with a fake Democratic candidate,” Krasner said.

“I’ve been a lifelong Democrat,” Vega said. “My mother would disown me if I wasn’t a Democrat.”

Perhaps one more example of prime Philly politics is the sole Republican candidate for DA, private attorney Charles Peruto, saying he’ll end his campaign if Vega, a Democrat, wins the primary.

“He would have accomplished what I set out to accomplish, and that is, replace Larry Krasner and his agenda,” Peruto said.

When it comes to the issues, Krasner is known for several progressive reforms he promised to bring to the DA’s office.

“And we’ve done that as well in terms of reducing mass incarceration, reducing mass supervision, protecting marginalized people,” Krasner said.

Vega says he’ll bring a commonsense approach to the DA’s office. But Krasner, the incumbent, has citywide name recognition that Vega is still working to build outside his South Philly neighborhood.

Eyewitness News asked several Philadelphians if they heard the name, Carlos Vega.

“I know Larry Krasner. I’m not really sure of Carlos Vega yet,” Kisha Hoist of South Philadelphia said.

“I’ve heard of Larry Krasner,” Shawn Mitchell of West Philly said. “The other guy, I have not.”

When asked who he thinks he’s going to vote for, Mitchell said Krasner.

Meanwhile, the Pennsylvania primary falls on May 18.