Although Hillary Clinton has not secured a public endorsement from President Barack Obama, she has stacked up a number of endorsements from his administration.

Earlier this year, Obama declared that he will not weigh into the Democratic primary race with an endorsement and will instead only campaign for the elected Democratic nominee, as long as they support "common-sense gun reform."

"There is no question that when it comes time, the president will be out there pounding the pavement for the nominee," White House Communications Director Jennifer Psaki told The New York Times. "But right now his focus, publicly and privately, is not on one candidate over another; it is on engaging the American people and about reminding them what is at stake."

In turn, Clinton has tuned to his administration's top officials for support in her run for the White House.

Back in October, the former first lady landed a major endorsement from U.S. Secretary of Housing and Urban Development Julian Castro. He also joined her at a campaign launch event for "Latinos for Hillary" in Texas, where he praised Clinton as the best candidate to tackle immigration reform.

In addition, Clinton recently accepted an endorsement from Transportation Secretary Anthony Foxx and made an appearance in South Carolina with former U.S. Attorney General Eric Holder. Meanwhile, Agriculture Secretary Tom Vilsack and Labor Secretary Tom Perez have also publicly declared their support.

"As someone who has had a front row seat, I sure as hell don't want to see the progress we made go backward," Perez said during a visit to a Las Vegas union office in December, according to The Associated Press. "And that's why, folks, I'm going to say I'm proud as hell of the fact that I have had the privilege of working for Barack Obama and I'm proud as hell to endorse Hillary Clinton to be the next president of the United States."

Experts say that the Clinton campaign is strategically leveraging these high-level endorsements to boost her appeal to Obama loyalists. She has also tried to depict Democratic rival Bernie Sanders as anObama adversary by pointing out that he suggested Obama face a second-term primary challenge in 2011. Sanders has also publicly criticized Obama for taking donations from Wall Street, notes Clinton.

Sanders, in turn, has said he understands why White House officials are backing Clinton. But as long as Obama and Vice President Joe Biden don't chime in, he's appears to be okay with it.

"There are Clinton people in the White House who clearly would like to see Hillary Clinton nominated," said the Vermont senator. "I understand that, and I simply hope that they will be as fair-minded as they can be," he said, adding, "I take President Obama and Vice President Biden at their word, they're not going to be tipping the scales here."