The FBI investigation into Hillary Clinton’s emails will likely carry into the middle of the campaign season, and it’s her top aides who could be in the most trouble, former FBI and national security officials told The Hill.

Most of the emails marked classified on the former secretary of state’s private server were sent to her by top State Department aides, noted Bradley Moss, a lawyer who specializes in national security and protection of classified information.

“If I’m in Clinton’s campaign, I’m more worried if am Cheryl Mills, Huma Abedin or Jake Sullivan than if I’m Hillary Clinton,” Moss told The Hill.

Democratic Presidential hopeful Hillary Clinton (R) gestures next to Huma Abedin after the second Democratic presidential primary debate in the Sheslow Auditorium of Drake University on November 14, 2015 in Des Moines, Iowa. AFP PHOTO/ MANDEL NGAN (Photo credit should read MANDEL NGAN/AFP/Getty Images)

Democratic presidential hopeful Hillary Clinton gestures next to Huma Abedin, left, after the second Democratic presidential primary debate Nov. 14 in the Sheslow Auditorium of Drake University in Des Moines. (Mandel Ngan/AFP/Getty Images)

Abedin, Mills and Sullivan were top Clinton aides at the State Department. Abedin and Sullivan now hold positions in Clinton’s presidential campaign.

More than 1,300 emails from Clinton’s private server were marked as classified, some at the highest level. Further, the FBI has reportedly expanded the investigation into how the State Department’s work intersected with the Clinton Foundation.

“I don’t know that there’s any magical cutoff date,” said Ron Hosko, the FBI’s former assistant director of the criminal investigative division and 30-year veteran, who is now the president of Law Enforcement Legal Defense Fund.

“I think the clock ticks louder every day,” Hosko said. “I’m sure they’re all incredibly sensitive to it.”

In December, FBI Director James Comey told the Senate Judiciary Committee that he would be “competent,” “honest” and “independent” and that “we don’t give a rip about politics.”

As the probe drags, this could be a problem for the Clinton campaign.

“More likely, it’s going to sour some of those folks in the middle,” Doug Roscoe, a political science professor at the University of Massachusetts Dartmouth, told The Hill. “Having to be in the news talking about this investigation takes her off-message.”