The ever-expanding field of Democratic presidential candidates includes a number of fresh faces, but it is the oldest living former president who is providing significant influence.

President Jimmy Carter, 94, has already met with 2020 hopefuls including South Bend, Ind., Mayor Pete Buttigieg, Minnesota Sen. Amy Klobuchar, and New Jersey Sen. Cory Booker. His ideas and his character are serving as models.

FORMER PRESIDENT JIMMY CARTER RELEASED FROM HOSPITAL FOLLOWING HIP SURGERY

"He won because he worked so hard, and he had a message of truth and honesty. I think about him all the time," Klobuchar told the Associated Press. She believes Carter, who served one term from 1977-1981, was "ahead of his time" when it came to issues such as climate change and health care.

Booker called Carter a "guiding light and inspiration." Buttigieg described him as "an extraordinary person." Even President Trump has consulted with Carter about issues such as relations with China. Each of them said the discussion was friendly.

Carter, in the past, has supported different Democratic candidates, stating that in 2016 he voted for Vermont Sen. Bernie Sanders in the 2016 Democratic primary. While he sided with the Democratic Socialist over Hillary Clinton, he has warned that if Democrats put forward "too liberal a program," it could lead to Trump being re-elected -- something Carter himself failed to do.

Carter was defeated by Ronald Reagan by a wide margin, after his presidency was mired by an Iran hostage crisis and high unemployment.

"Their administration was not perfect," Klobuchar admitted.

JIMMY CARTER SAYS TRUMP CALLED HIM TO DISCUSS US-CHINA RELATIONS

Booker, Buttigieg, and Klobuchar all met with Carter while attending sessions of his weekly Sunday School class at Maranatha Baptist Church. They have been proud to promote these meetings, unlike other candidates' meetings with past presidents like Bill Clinton and Barack Obama, which were only disclosed through anonymous tips.

Carter was scheduled to teach this weekend, but ended up having to back out as he recovers from hip replacement surgery. The former president broke his hip during a fall at his home on Monday, and was released from Phoebe Sumter Medical on Thursday.

The Associated Press contributed to this report.