Senator Bernie Sanders is refusing to endorse his Senate colleague Dianne Feinstein in the upcoming California primaries.
Sanders told The Hill on Friday he’s staying out of this race because “It’s an issue for the people of California.”
The former presidential candidate has publicly endorsed other Democrats on the campaign trail.
On Thursday, he announced his support for liberal candidate Marie Newman in her Illinois primary challenge against a seven-term Democratic incumbent.
Bernie Sanders through the years
Bernie Sanders through the years
Senator Bernie Sanders, an independent from Vermont and 2016 Democratic presidential candidate, speaks during an event in Iowa Falls, Iowa, U.S., on Monday, Jan. 25, 2016. With a week to go until the Iowa caucuses and the Democratic presidential race there in a virtual dead heat, Hillary Clinton and Sanders are mapping out divergent paths toward winning the first votes of the nomination process. Photographer: T.J. Kirkpatrick/Bloomberg via Getty Images
Washington, UNITED STATES: Newly-elected senators meet with Senate Minority Leader Harry Reid (R), D-NV, in Washington, DC 13 November 2006. From left are: Senator-elect James Webb, D-VA, Senator-elect Bernie Sanders, I-VT, Senator-elect Amy Klobuchar, D-MN, and Reid. AFP PHOTO/Karen BLEIER (Photo credit should read KAREN BLEIER/AFP/Getty Images)
US Congressman Elliot Engel (L) takes pictures next to US Senator Bernie Sanders after being dressed as Bouale leaders by public notaries of the Kouadioyaokro village, 150 km from Abidjan, 09 November 2008. US Senators Tom Harkin and Bernie Sanders visit comes ahead of a July 2008 certification deadline to ensure cocoa heading to the United States -- the third largest importer of Ivorian cocoa -- has not been produced with child labour. AFP PHOTO/ISSOUF SANOGO (Photo credit should read ISSOUF SANOGO/AFP/Getty Images)
COLUMBIA, SC - APRIL 25: Potential Democratic presidential candidate Sen. Bernie Sanders (R) (I-VT) delivers remarks at the South Carolina Democratic Party state convention April 25, 2015 in Columbia, South Carolina. Sanders joined former Maryland Gov. Martin O'Malley and former Sen. Lincoln Chafee in speaking to the convention. (Photo by Win McNamee/Getty Images)
WASHINGTON, DC - APRIL 20: U.S. Sen. Bernie Sanders (I-VT) participates in a 'Don't Trade Our Future' march organized by the group Campaign for America's Future April 20, 2015 in Washington, DC. The event was part of the Populism 2015 Conference which is conducting their conference with the theme 'Building a Movement for People and the Planet.'
(Photo by Win McNamee/Getty Images)
U.S. Senator Bernie Sanders, an Independent from Vermont and 2016 U.S. presidential candidate, greets supporters during a campaign rally in Madison, Wisconsin, U.S., on Wednesday, July 1, 2015. Sanders said he had attracted 200,000 donors as of mid-June and his campaign had raised $8.3 million online through June 17, according to FEC filings by ActBlue, the fundraising platform that he and some other left-leaning candidates and causes use. Photographer: Christopher Dilts/Bloomberg via Getty Images
PORTLAND, ME - JULY 6: Vermont Sen. Bernie Sanders speaks at the Cross Insurance Arena while campaigning in the Democratic presidential primary. (Photo by Derek Davis/Portland Press Herald via Getty Images)
Supporters hold up signs at a campaign rally for Senator Bernie Sanders, an Independent from Vermont and 2016 U.S. presidential candidate, in Madison, Wisconsin, U.S., on Wednesday, July 1, 2015. Sanders said he had attracted 200,000 donors as of mid-June and his campaign had raised $8.3 million online through June 17, according to FEC filings by ActBlue, the fundraising platform that he and some other left-leaning candidates and causes use. Photographer: Christopher Dilts/Bloomberg via Getty Images
PORTLAND, ME - JULY 6: Vermont Sen. Bernie Sanders speaks at the Cross Insurance Arena while campaigning in the Democratic presidential primary. Sen. Bernie Sanders greets supporters after speaking in Portland. (Photo by Derek Davis/Portland Press Herald via Getty Images)
PHOENIX, AZ - JULY 18: U.S. Sen. Bernie Sanders (I-VT) speaks to the crowd at the Phoenix Convention Center July 18, 2015 in Phoenix, Arizona. The Democratic presidential candidate spoke on his central issues of income inequality, job creation, controlling climate change, quality affordable education and getting big money out of politics, to more than 11,000 people attending. (Photo by Charlie Leight/Getty Images)
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Feinstein, who's served five consecutive Senate terms, failed to secure an endorsement at California’s state Democratic convention last month with nearly two-thirds of the party's delegates voting against her, according to the LA Times.
The Hill reports that Feinstein was one of Hillary Clinton’s biggest supporters, urging Bernie Sanders to drop out of the presidential race.
According to Politico, Feinstein’s centrist approach has caused her to maintain a troubled relationship with the liberal wing of her party.
Senator Dianne Feinstein through the years
Senator Dianne Feinstein through the years
San Francisco's mayor Dianne Feinstein smiling and reviewing a document in her city hall office.
UNITED STATES - JANUARY 11: Sen. Dianne Feinstein, D-Calif., talks with reporters before a Senate Judiciary Committee markup in Dirksen Building on the 'Amy, Vicky, and Andy Child Pornography Victim Assistance Act of 2017' and judicial nominations on January 11, 2018. (Photo By Tom Williams/CQ Roll Call)
San Francisco Mayor & Dem. gubernatorial hopeful Dianne Feinstein speaking on telephone in private box during NFL game between San Francisco 49ers & Seattle Seahawks; looking at aide. (Photo by Kim Komenich/The LIFE Images Collection/Getty Images)
California Governor Gray Davis (L) chats with Senator Dianne Feinstein
(D-CA) on his campaign plane during a three-day tour of California,
October 4, 2003. Davis faces a recall election October 7. REUTERS/Lucy
Democratic Senator Dianne Feinstein is chair of the Senate Intelligence Committee. Her staff is responsible for spearheading the 6,000-page report set to be released Tuesday, Dec. 9, 2014, on the interrogation tactics used by the CIA during the George W. Bush years, which President Obama and others have labeled as torture.
US President 's first Supreme Court nominee, Ruth Bader Ginsburg (left) is greeted by the first two women to serve on the Senate Judicary Committee - Dianne Feinstein (D-CA) and Carol Moseley-Braun (D-IL), right - on July 20 prior to the opening of Ginsburg's confirmati on hearings on Capitol Hill
WASHINGTON, DC - NOVEMBER 20: Committee Chairman Sen. Dianne Feinstein (D-CA) administers the oath for Acting Director at the National Counterterrorism Center Nicholas Rasmussen during his confirmation hearing before the Senate (Select) Intelligence Committee on November 20, 2014 on Capitol Hill in Washington, DC. Rasmussen has been nominated to lead the National Counterterrorism Center and he will become the next director if confirmed by the Senate. (Photo by Alex Wong/Getty Images)
U.S. Senator Dianne Feinstein (D-CA) (L) welcomes U.S. Supreme Court nominee Judge Neil Gorsuch (R) in her office on Capitol Hill in Washington, U.S., February 6, 2017. REUTERS/Jonathan Ernst
Senator Dianne Feinstein, a Democrat from California, talks to reporters after a private meeting the U.S. Capitol Building in Washington, D.C., U.S., on Thursday, Nov. 13, 2014. U.S. Senate Democrats plan to elevate first-term Massachusetts Senator Elizabeth Warren to their leadership ranks on an expanded communications and policy committee led by third-ranking Democrat Charles Schumer. Photographer: Andrew Harrer/Bloomberg via Getty Images
WASHINGTON, DC - NOVEMBER 12: U.S. Sen. Dianne Feinstein gets off a escalator at the U.S. Capitol building November 12, 2014 in Washington, DC. Congress returned to work today following last week's mid-term election break. (Photo by Mark Wilson/Getty Images)
Ranking Member Sen. Dianne Feinstein (D-CA) speaks with Sen. Patrick Leahy (D-VT) during a meeting of the Senate Judiciary Committee to discuss the nomination of Judge Neil Gorsuch to the Supreme Court on Capitol Hill in Washington, D.C., U.S., April 3, 2017. REUTERS/Aaron P. Bernstein
WASHINGTON, DC - JUNE 05: Committee chairman Sen. Dianne Feinstein (D-CA) (L) listens to an aide during a hearing before the Senate (Select) Intelligence Committee June 5, 2014 on Capitol Hill in Washington, DC. The hearing was focused on 'Foreign Intelligence Surveillance Act (FISA) Reforms' and H.R.3361 the 'USA FREEDOM Act.' (Photo by Alex Wong/Getty Images)
Ranking member Sen. Dianne Feinstein (D-CA) and Senate Judiciary Committee Chairman Chuck Grassley (R-IA) preside over the Senate Judiciary Committee confirmation hearing for Supreme Court nominee Neil Gorsuch (not pictured) on Capitol Hill in Washington, U.S., March 20, 2017. REUTERS/James Lawler Duggan
Senator Dianne Feinstein (D-CA) speaks to reporters after the Senate approved $15.25 billion in aid for areas affected by Hurricane Harvey along with measures that would fund the federal government and raise its borrowing limit on Capitol Hill in Washington, U.S., September 7, 2017. REUTERS/Joshua Roberts
Senate Judiciary Committee ranking member Sen. Dianne Feinstein (D-CA) speaks during FBI Director James Comey's appearance before a Senate Judiciary Committee hearing on "Oversight of the Federal Bureau of Investigation" on Capitol Hill in Washington, U.S., May 3, 2017. REUTERS/Kevin Lamarque
President Bill Clinton holds hands with US. Senator Dianne Feinstein (L) and California Democratic Governor Candidate Kathleen Brown (R) November 4 at a Democratic party rally on the steps of Los Angeles City Hall. Clinton urged voters to elect Brown and re-elect Fienstein, saying he needs them on his team
California State Assemblyman and Democratic Party Congressional candidate Mike Honda raises his arm along with California Senator Dianne Feinstein (D/CA) (L) at a campaign rally at Honda headquarters in San Jose, California, on November 1, 2000. Honda is locked in a tight race with Republican Party candidate Jim Cunneen to represent California's 15th Congressional District. The seat is being vacated by Republican Representative Tom Campbell who is running for the U.S. Senate against Feinstein.
Senator Dianne Feinstein addresses supporters November 7 at a pre-election day rally at her campaign headquarters
U.S. Senator Dianne Feinstein (D-CA) laughs during an election party in San Francisco, California, November 7, 2006. REUTERS/Kimberly White (UNITED STATES)
(Original Caption) San Diego: On the end of a two-day, 5-city campaign tour, former San Francisco Mayor Dianne Feinstein announces her intention to seek the Democratic nomination for California governor in the June 5th primary election. Speaking to the San Diego media on the issues, she challenged opponent Calif. Atty. Gen. John Van de Kamp to a series of 6 debates.
MEET THE PRESS -- Pictured: (l-r) Sen. Dianne Feinstein (D-CA) appears on 'Meet the Press' in Washington, D.C., Sunday, Dec. 3, 2017. (Photo by: William B. Plowman/NBC/NBC NewsWire via Getty Images)
WASHINGTON, DC - DECEMBER 6: (L to R) Committee chairman Sen. Chuck Grassley (R-IA), ranking member Sen. Dianne Feinstein (D-CA), and Sen. Patrick Leahy (D-VT) talk with each other during a Senate Judiciary Committee hearing concerning firearm accessory regulation and enforcing federal and state reporting to the National Instant Criminal Background Check System (NICS) on Capitol Hill, December 6, 2017 in Washington, DC. (Photo by Drew Angerer/Getty Images)
Senator Dianne Feinstein, a Democrat from California and ranking member of the Senate Judiciary Committee, listens during a hearing with Jeff Sessions, U.S. attorney general, not pictured, in Washington, D.C., U.S., on Wednesday, Oct. 18, 2017. Sessionsï¿½told senators he won't answer questions about his conversations with Presidentï¿½Donald Trumpï¿½over the firing of FBI Directorï¿½James Comey. Photographer: Zach Gibson/Bloomberg via Getty Images