But Kim’s win was not a surprise. The congressmember launched his political career in his native Burlington County — landing an upset
victory in a Republican-leaning district in 2018 that sent him to the House — and received a standing ovation after speaking here.

So the question headed into the South Jersey county’s Democratic convention on Saturday was not whether Kim would win, but by how much.

“I will tell you I’m really proud of that number I’m getting for me to be able to receive over 90 percent of the vote in this county. That’s a big number,” Kim told reporters after it was announced he won. “We’re feeling this level of energy in all 21 counties. You know, I was up in Jersey City yesterday. Hundreds of people showed up, hundreds of people in Bergen County the day before. So we’re just really excited about this.”

Murphy could now choose to run on the primary ballot with other candidates in Burlington County, like Democratic Assemblymember Carol Murphy — who is running for the House seat Kim is vacating and lost the party endorsement here to Assemblymember Herb Conaway — although it is unclear whether that will happen. Carol and Tammy Murphy are not related.

When asked about running with the other Murphy in Burlington County to appear more prominently on the ballot, Tammy Murphy told reporters that “the thought hasn’t even crossed my mind.”

New Jersey’s Democratic primary is June 4. But primary races here are largely shaped by winning county party endorsements before Election Day, which typically translate to favorable positioning on the primary ballot — known in New Jersey as “the line,” in which party-backed candidates all appear together in a group instead of running by office, like many other states do.

Every county party in New Jersey has a different endorsement process for the line: Some are top-down, where a local party boss bestows the county endorsement, while others host party conventions where rank-and-file Democrats — like party precinct leaders, or county committee members, as they’re called in the state — vote by secret ballot, as members in Burlington County did on Saturday.

Kim said that he had been making the case to county chairs in Essex, Middlesex and Union for a secret ballot, adding that he saw the line as a liability for Democrats. “I think people see the broken system, and we’re gonna lose credibility in terms of this primary.”

During the convention — in a surprise move — state Sen. Troy Singleton, one of the most influential Democrats in the county, called to abolish the county line system, saying that “at some point we should just have everybody … in one block all across the state.”

Speaking with reporters afterwards, Singleton said he would support legislation to eliminate the state’s unique ballot positioning. He joins a growing number of Democrats, including gubernatorial candidate Steven Fulop, who say the line should be eliminated.

“It’s opportune for us to lead as Democrats with this idea that we do not need the organizational lines to ensure that we have the best candidate,” Singleton, a Kim supporter, said.

Tammy Murphy — who is the wife of Gov. Phil Murphy — has relied heavily on top-down support from party leaders across the state. County leaders from Democratic strongholds quickly endorsed her, making her the favorite to win the party nomination.

And that party backing could still prove enough for Murphy to win. But at this early stage, Kim has captured the support of rank-and-file Democrats. Earlier this month he won the convention of Monmouth County Democrats by a landslide and is leading in public opinion polls against Murphy. The next party convention is Sunday in Hunterdon County, a rural swath of the western part of the state.

“I’m just playing according to the rules as everybody is, so I would just say we’re all doing the same thing,” Murphy said when asked about her thoughts on the county line process. “ I think everybody’s trying to do their best within the system that we have.”

There was conversation in the lead-up to the Burlington convention of having candidates share the county line, but that didn’t come into fruition.

Kim has also alleged that the governor himself had weighed in in support of a shared line, although the Murphy campaign has denied that. Singleton said that “the governor never spoke to me about that.”

Tammy Murphy told reporters that she was not aware of shared lines efforts.

According to state data, Burlington County has just short of 140,000 Democrats, around 5.6 percent of the state’s total. Monmouth County, where Kim won the party endorsement, also makes up 5.6 percent of the statewide Democratic electorate.

Menendez, who has been accused by federal authorities of corruptly using his office, has not said if he would seek reelection. He did not compete in the convention.