The Federal Bureau of Investigation is losing confidence in Hillary Clinton and her mishandling of a private email server, a New York Post columnist suggested on Sunday.

"FBI chief James Comey and his investigators are increasingly certain presidential nominee Hillary Clinton violated laws in handling classified government information through her private e-mail server," Charles Gasparino said career agents had told him.

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"Some expect him to push for charges, but he faces a formidable obstacle: the political types in the Obama White House who view a Clinton presidency as a third Obama term," Gasparino added. "With that, agents have been spreading the word, largely through associates in the private sector, that their boss is getting stonewalled, despite uncovering compelling evidence Clinton broke the law."

Clinton is facing a federal indictment over charges that she mishandled classified information during her tenure as secretary of state by storing it on a personal email server. The FBI earlier this month granted immunity to Bryan Pagliano, a Clinton aide who helped to establish the server in the basement of her Chappaqua, New York home, as part of its investigation into the matter.

"You don't start granting people close to Clinton immunity unless you are seriously looking at charges against your target," Gasparino quoted one former official as saying.

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The fact that Pagliano received immunity, experts have noted, could signal that a grand jury has already been impaneled, though it depends on the details of the agreement. Those details are presently unclear.

"I'm also told Comey and his team increasingly doubt Clinton's story," Gasparino said. "Most officials know private email servers are easier to hack into than secure government servers. They also know that even documents not labeled 'classified' may be top secret."

"Law-enforcement sources also say Comey's record as a prosecutor shows he has zero tolerance for such abuses," Gasparino wrote. "However, FBI sources say he has no backing from President Obama and Attorney General Loretta Lynch to recommend charges against the former secretary since a Clinton presidency may be the best chance to preserve the Obama legacy."

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"That leaves Comey in a bind: Does he do what is politically expedient and deny the reality that Clinton's e-mail server activities violated the law, or follow the evidence to wherever it takes him?" he added.