COLUMBIA — They call lawmakers on their cellphones to try to make a personal connection. They offer to help with their own future campaigns to return the favor.

Their staffers, particularly those who have worked in South Carolina before, seek to leverage their own relationships to win them over to the cause.

While the results of South Carolina's Democratic presidential primary will ultimately be decided by rank-and-file voters, the candidates have separately been engaged in a yearlong battle to cultivate influential local officials in hopes of adding their imprimatur to the campaigns — and with it, ideally, the votes of their constituents.

As College of Charleston political science professors Gibbs Knotts and Jordan Ragusa explain in a new book on the First in the South primaries, endorsements "have often played a key role in a candidate's performance in South Carolina" and can serve as a predictor of their electoral success in the state.

Former Vice President Joe Biden is pacing the field when it comes to that metric, capitalizing on the decades of relationships he's built in the state while also winning over some newer faces on the political scene to demonstrate his broad support from the state's Democratic establishment.

His dozens of supporters, more than all the other candidates combined, range from the 87-year-old Dick Riley, a former S.C. governor and U.S. education secretary who worked with Biden during his time in the Clinton administration, to the 30-year-old state Rep. Marvin Pendarvis of North Charleston.

Adding to those elected officials is more than 100 faith leaders from every corner of the state, giving Biden some valuable voices coming from the pulpit on Sundays.

U.S. Sen. Bernie Sanders has won the backing of eight African American state lawmakers, including some who previously supported him in his 2016 campaign, including state Reps. Terry Alexander and Justin Bamberg.

Sanders has also touted the endorsements of multiple mayors and local officials, including Stephen Wukela of Florence and Brendan Barber of Georgetown, as well as a group of Latino activists who could help boost Sanders among the state's small but growing Hispanic population.

Though a relative newcomer to campaigns, billionaire businessman Tom Steyer has found more success courting S.C. officials than several more established figures, winning endorsements from five state House members. He made one of them — Legislative Black Caucus chairman Jerry Govan — a senior adviser on his campaign.

Recently, Steyer picked up his first endorsement from the state Senate in John Scott of Columbia, as well as S.C. Democratic Party black caucus Chairman Johnnie Cordero.

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U.S. Sen. Elizabeth Warren has two lawmakers in her corner from the crucial Democratic county of Richland in state Reps. Wendy Brawley and Kambrell Garvin, as well as several local officials from around the state.

In an unusual twist, one of South Carolina's most prominent Democratic officials — Columbia Mayor Steve Benjamin — is backing a candidate who won't even appear on the state's ballot: former New York City Mayor Michael Bloomberg, who decided to focus on states with primaries later in the cycle after entering the race late.

None of the other seven remaining candidates have landed any notable S.C. supporters.

Perhaps the two biggest prizes remain up for grabs.

Neither of South Carolina's Democratic congressmen, Jim Clyburn of Columbia and Joe Cunningham of Charleston, have endorsed a candidate — and it remains unclear whether they will before the state's Feb. 29 primary.

Not all elected officials buy into the endorsement game at all.

State Rep. Gilda Cobb-Hunter, the longest-serving member of the S.C. House, makes clear from the outset of every presidential campaign that she won't be offering an endorsement because she believes voters should do their own homework on the candidates rather than simply following her lead.

"I think endorsements tend to do more for the person doing the endorsing than they do for the candidate, particularly if the endorsement does not come with a real constituency," Cobb-Hunter said.

The limitations of endorsements have also been demonstrated through some of the candidates who dropped out.

Most notably, U.S. Sens. Kamala Harris of California and Cory Booker of New Jersey quickly earned the support of several S.C. lawmakers and activists, like CNN commentator Bakari Sellers for Harris and state Rep. John King for Booker, only to see their campaigns ultimately fizzle out.

As far as the remaining campaigns were concerned, the departure of Harris and Booker simply opened up more potential endorsers to be wooed once again.