Sen. Lindsey Graham's Democratic opponent in this fall's U.S. Senate election in South Carolina has enlisted a crew of heavy-hitting bundlers to raise large amounts of cash.

Jaime Harrison, the former chairman of the state's Democratic Party, has the backing of several big-dollar fundraisers as he seeks to unseat the powerful Republican lawmaker and ally of President Donald Trump, according to people with direct knowledge of the matter. These people declined to be named as the decisions have yet to be made public by the campaign.

According to the people, Harrison's list of bundlers includes Jon Henes, a senior partner at legal juggernaut Kirkland & Ellis; Brian Mathis, a founding partner at investment firm Pine Street; Mike Kempner, the CEO of public relations juggernaut MWWPR; Melissa Prober, a senior associate counsel at the New York Genome Project; Sarah Min, a digital media consultant, and Jonathan Klein, a partner at DLA Piper.

Bundlers often help arrange fundraising events and reach out to prospective donors to encourage them to give to the campaigns they're supporting.

The development comes as Harrison's campaign reported outraising Graham in the first quarter of 2020, $7.3 million to $5.5 million, according to Federal Election Commission filings. Graham, however, has slightly more cash on hand, with $12 million compared with Harrison's $8 million.

The Senate race in South Carolina is still labeled as "safe Republican" by Larry Sabato's Crystal Ball. Harrison has been running on lowering the cost of health care, expanding the child care tax credit and supporting paid family and sick leave.

A spokesman for Harrison and most of the party donors did not return repeated requests for comment. Min could not be reached.

All campaigns have been forced to go virtual, and Harrison has been one of the candidates leading the way for Democrats with town halls over Facebook.

These fundraisers for Harrison assisted Sen. Kamala Harris, D-Calif., when she was running for president. Henes was Harris' national finance chair during her campaign.

Henes' efforts for Harrison include a memo sent to his donor network, imploring donors to tune in to a virtual meet and greet featuring Sen. Cory Booker, D-N.J., which is scheduled to take place on Tuesday.

"This video call is an opportunity to meet and get to know a rising star in national Democratic politics as he takes on Senator Lindsey Graham," Henes wrote in the note, which also gave potential supporters a glimpse into Harrison's upbringing and career in politics.

Booker and Harris are two of only three black members of the Senate. The other is Tim Scott, a Republican of South Carolina. Harrison is also black.

Harris featured Harrison in one of her "Meet the Candidates" episodes, which allowed her to introduce him to many of her supporters and donors. The meeting took place over Zoom in early April and some of Harris' previous bundlers were inspired to sign on to back Harrison in the wake of the call, a person familiar with the efforts said.

Beyond Harris, most of these donors have helped raised money for Joe Biden, the apparent Democratic nominee for president, who recently endorsed Harrison's candidacy, and former President Barack Obama.

Harrison has ties to leaders in the party. He was once an aide to South Carolina kingmaker and U.S. Rep. James Clyburn. Harrison also once ran to be the chairman of the Democratic National Committee but eventually dropped out of the race to later endorse Tom Perez.