Richter researched the district‘s voting patterns, demographics and electoral history.

”I had an almost 2-inch thick binder of documents,” he said in a recent interview. “I surprised myself and got an A on it.”

Now Richter is putting his academic research to real-life use as he — along with three other Republicans — seek the district’s GOP nomination.

But Van Drew changed the entire dynamic of the race when he switched parties and was quickly considered the frontrunner.

Van Drew, who did not respond to a request for comment, had been planning to seek reelection as a Democrat, but saw his support plunge into in the 20s when he announced he would vote against impeaching Trump. After a frantic and unsuccessful effort to shore up party support — Democratic leaders were abandoning him — Van Drew switched to the GOP and, in a formal announcement, pledged his “undying support” to Trump as he sat next to the president in the Oval Office.

Richter quickly found his top political consultants and much of his staff leaving his campaign so as not to alienate the National Republican Congressional Committee, which is backing the newly-minted GOP incumbent.

“The NRCC basically pulled them in and said, ‘You need to be working for a Republican incumbent, and if you work for a Republican running against an incumbent, you’ll essentially be blackballed from doing further work,” Richter said.

Chris Russell, who had been one of Richter’s consultants, said his firm’s decision not to work against a party-endorsed incumbent was “our choice” because “we felt it was a conflict.“ NRCC spokesperson Michael McAdams said in a statement the committee “doesn’t blacklist consultants.”

The 2nd District includes all or parts of eight counties and stretches from the Jersey Shore to the Delaware River. While New Jersey’s more affluent districts in the north have turned against Trump, much of the 2nd has embraced him. Trump carried the district in 2016, even though former President Barack Obama won it in 2008 and 2012.

“I understand the decision of the president“ to openly support Van Drew, Richter said. “It benefited the president during impeachment week when he needed a positive story, and a Democrat flipping to the Republican Party over impeachment is a good story. The problem is the narrative isn’t accurate. Van Drew switched parties because he was going to lose, and this is an attempt to save his own job.”

Also running for the GOP nomination are Brian Fitzherbert, a defense contractor, and Bob Patterson, a former Trump administration Social Security aide who edited a conservative academic journal.

Fitzherbert, 30, said his background as a project manager and engineer in the aerospace industry makes him a good fit for the district.

“The district has a lot of assets that Frank LoBiondo was instrumental in getting off the ground,” he said.

Patterson, 66, said he wants to boost manufacturing in South Jersey and supports a bill that would move many federal agencies away from the Washington, D.C., area.

“I would see the possibility of bringing two or three agencies to South Jersey, and with that, all these jobs,” he said.

Despite his reputation as a conservative Democrat who bucked the party on impeachment, Van Drew typically cast major votes with his former party during his first year in Congress and has a record of supporting abortion rights.

Van Drew has broken with Trump on several issues: He opposed offshore drilling and the military’s ban on transgender soldiers, and favored a $15 federal minimum wage. His congressional record was arguably more liberal than his record as a state lawmaker, when he voted against a $15 minimum wage and against same-sex marriage.

Among New Jersey’s Democratic House delegation, several members have voted in line with the president’s position more often than Van Drew, according to the data-driven website FiveThirtyEight.

Van Drew has long, deep roots in the 2nd District, where he began his political career as a Cape May County freeholder and represented part of it for nearly two decades in the state Legislature.

The other three Republicans claim connection to the district, though they have all recently lived somewhere else.

Richter was a longtime Princeton resident, which is far outside the district, and rented a home less than two years ago in Miami Beach, Fla., where he planned to move and where he voted in 2018 before ultimately deciding to stay in New Jersey. He moved into the district in the fall, while his children continue to go to school in Princeton.

Fitzherbert, who grew up in North Jersey, has owned a home in the district since he was 23 but has moved around the country in recent years “as a result of the demands of the job,” and only began voting in the 2nd District in June 2018.

Patterson, who grew up in a different part of South Jersey, ran unsuccessfully for Congress in New Jersey’s neighboring 1st District in 2016 after living in Virginia for about 20 years.

Prior to Van Drew, Richter had been the main target of Fitzherbert and Patterson. They both pointed out that his company, Hill International, had hired former Vice President Joe Biden’s brother as an executive of a subsidiary around the same time it secured a housing contract in Iraq, which ultimately fell through.

Richter said it was his father’s decision to hire Biden‘s brother, and that he had warned against it. “The whole time we were in this business, I was pushing my dad to end it. And finally after several years of losses, he finally ended it and shut the whole thing down,” he said.

Fitzherbert’s campaign pointed out that Richter’s voting record was spotty, and that he had not voted in nearly half the primary and general elections in recent years.

Fitzherbert and Patterson have potential weaknesses as well.

Fitzherbert has struggled to raise money, while Patterson has a history of controversial public statements, including favorably summarizing a study in a conservative journal in which he and a co-author wrote that using condoms “robs a woman of all these remarkable chemicals” found in semen.

That statement, along with Patterson’s writings that criticized women choosing careers over marriage and raising children, led to his resignation in 2012 as an adviser to then-Pennsylvania Gov. Tom Corbett after The Philadelphia Inquirer raised questions about them.

“I have written hundreds of articles over my career, and some of those articles dared to question or debunk liberal groupthink on many issues,” Patterson said. “In other cases, I was summarizing scientific findings of empirical studies that someone else conducted.”

With the support of Trump and the NRCC, Van Drew is the new frontrunner. Pressure will build on local leaders to back him as well, giving him the “party line,” which in most of the district bestows favorable ballot placement.

The fact that all three remain committed to the race poses another danger. Even if Republican primary voters are suspicious of Van Drew’s motives for fleeing the Democratic Party, they might split their votes among the three challengers.

In addition to Trump, Van Drew is being advised by former White House political director Bill Stepien, who worked for years as a New Jersey Republican operative, and managed by Ron Filan, a well-known Republican consultant in New Jersey.

Monmouth University pollster Patrick Murray suggested the primary may get less crowded if local Republican leaders fall in line behind Van Drew — something that’s already beginning with some local GOP chairs.

“Right now, it looks like it’s going to be crowded, but it could end up falling by the wayside if you have some key leaders ... coming out in support of a particular candidate,” Murray said. “If it happens to be Van Drew, you’re going to see the entire party get in line by the April filing deadline.”

The race won’t be over with the primary. Despite its Trump leaning, the 2nd District remains highly competitive, and Democrats plan to compete there. Three candidates — political science professor Brigid Harrison, Atlantic County Freeholder Ashley Bennett and environmentalist John Francis — are seeking the Democratic nomination.

“Certainly this leans Republican, and whoever the nominee is will be considered the favorite,’ but by how much of a favorite really depends on the presidential election,” Murray said.