Almost all the senators in the 2020 Democratic presidential field enjoy the support of their fellow home state Democratic senators, but California Sen. Dianne Feinstein, D-Calif., broke that mold with her endorsement of former Vice President Joe Biden over her fellow Californian, Sen. Kamala Harris.

Feinstein told the Washington Examiner Tuesday that she feels more loyal to Biden than Harris.

“I’ve known Joe Biden for 20 years. When he was chairman of the Judiciary Committee, he made me the first woman. We have a longstanding relationship that dates way back. I love Kamala, I appreciate her, but she has known about this for some time. But that’s what I’m going to do. I feel very loyal to him," Feinstein said.

Other senators, several of them, like Feinstien, 85, veteran lawmakers, either don't share the same bond with Biden, 76, or don't have the same sense of loyalty.

[ Related: Kamala Harris stumps Barr with question on whether Trump suggested an investigation]

Sen. Patrick Leahy, D-Vt., endorsed Sen. Bernie Sanders, I-Vt., as a “proven leader with a strong message” the day Sanders announced his candidacy. When Sen. Cory Booker, D-N.J., announced his candidacy,

Sen. Bob Menendez, D-N.J., said that Booker “makes a great friend, and will make an even greater president.” Sen. Tina Smith, D-Minn., was “proud to stand with” Sen. Amy Klobuchar, D-Minn., when Klobuchar announced her campaign, and Sen. Ed Markey, D-Mass., threw his support behind Sen. Elizabeth Warren, D-Mass, when she announced her candidacy.

The only other senator seeking the presidency without the support of a home-state Democratic senator is Sen. Kirsten Gillibrand, D-N.Y. Senate Minority Leader Chuck Shumer, D-N.Y., said in March that he will “stay out of the presidential” race. “Let's see who the best candidate is," he said.

Feinstein, on the other hand, not only threw her support behind Biden but also drew attention to the limited experience in national politics of Harris, 54. Harris was elected to the Senate in 2016. “She’s brand-new here, so it takes a little bit of time to get to know somebody,” Feinstein said in January.

[ Opinion: A potential weakness in Kamala Harris' California 'firewall']

Feinstein’s support of Biden rather than Harris underscores the difference between older factions of the Democratic Party and the new, aggressive, liberal wing. While the two senators vote together about nine times out of 10, according to ProPublica, Feinstein's approach to some controversial issues differs from Harris.

"A lot of the positions that Biden's taken that he's getting flak for, Feinstein's taken the same positions along the way," John Thomas, a Republican strategist in California, told the Washington Examiner.

There may been some history here as well.

When Harris was San Francisco district attorney, her handling of a 2004 killing of a police officer by a gang member prompted sharp criticism from Feinstein. Harris said that she would not seek the death penalty for the killer, and in response , Feinstein said that if she had known that Harris was against the death penalty, she probably wouldn’t have endorsed her for district attorney.

[ Also read: Biden brags about his time in 'the hood']

Feinstein also disagreed with comments Harris made about "Medicare for all," which would eliminate private health insurance, at a CNN town hall in January.

“Who of us has not had that situation, where you’ve got to wait for approval and the doctor says well, ‘I don’t know if your insurance company is going to cover this.’ Let’s eliminate all of that. Let’s move on,” Harris said at the town hall.

In response, Feinstein said she was "not there” on eliminating private health insurance.

"Feinstein respects seniority," Thomas said, noting that she is also very relationship-oriented and is more familiar with Biden. "Almost stroking her own ego, she needs to go with someone who has a comparable level of seniority."

Harris on Tuesday ignored questions from the Washington Examiner in the halls of the Capitol, and her campaign and Senate office did not return requests for comment.