The departure of National Security Adviser John Bolton this week was the culmination of months of sharp-elbowed conflicts between the foreign policy hawk and officials at all levels of the Trump administration -- with sources saying that even a quietly influential aide to the White House chief of staff was lobbying for his ouster.

President Trump acknowledged the broader conflicts as he briefly talked with reporters about the unceremonious exit.

“He made some big mistakes. ... John wasn’t in line with what we were doing,” Trump said Wednesday in the Oval Office. Trump recalled that he told Bolton, “You aren’t getting along with a lot of people and a lot of people don’t like your tactics and your ideas and I would like you to resign.”

TRUMP OUSTS NATIONAL SECURITY ADVISER JOHN BOLTON, SAYS THEY 'DISAGREED STRONGLY' ON POLICY

Bolton disputes Trump's version of events, maintaining he offered to resign before the announcement. But the internal tensions were on full display in the aftermath. Numerous reports have emerged of clashes over a range of issues between Bolton and Secretary of State Mike Pompeo, who publicly backed Trump's decision on Bolton.

And according to sources close to the administration, another figure – Rob Blair, who serves as Chief of Staff Mick Mulvaney’s national security adviser – was a key figure in Bolton’s departure. Blair, whose position isn’t a formal one inside the White House, has worked to “put Bolton on notice” while using his connections with Mulvaney to get access to the Oval Office, sources said.

Sources close to the matter told Fox News that Blair has even been lobbying Trump to name him to replace Bolton. However, he does not enjoy the public recognition or the deep national security resume that other potential candidates have.

Trump said Thursday that as many as 15 candidates are competing for the job.

Before joining Mulvaney’s staff, Blair was an associate director of national security programs at the Office of Management and Budget and previously worked as a staffer for a subcommittee and a regional adviser for the State Department's Office of International Health Affairs.

Attempts to reach Blair for comment were not successful.

It has also been reported that Bolton frequently clashed with Pompeo, especially over a plan from Pompeo and Trump to negotiate a peace deal with the Taliban in Afghanistan and withdraw U.S. troops from the war-torn nation after almost 18 years of conflict. Bolton argued against a complete troop withdrawal and negotiations with the terror group.

While Trump ultimately canceled recent talks following an attack that left a U.S. serviceman dead, aides in support of negotiating blamed Bolton for public leaks about his opposition.

FEVERED SPECULATION OVER JOHN BOLTON'S REPLACEMENT AS NATIONAL SECURITY ADVISER

The secretary of state also reportedly clashed with Bolton over the former’s softening stance toward sanctions against Iran, and the president has begun to drift away from Bolton’s hardline stances toward global hotspots like North Korea and Venezuela.

Still, Trump maintained Thursday that he, not Bolton, held the hardline stance on such issues, tweeting, "In fact, my views on Venezuela, and especially Cuba, were far stronger than those of John Bolton. He was holding me back"!

Pompeo has remained largely quiet about Bolton’s departure from the influential post, admitting only that the two previously had disagreements but refusing to answer questions on the White House’s “inner workings.”

“There were many times Ambassador Bolton and I disagreed, that’s to be sure,” Pompeo said. “But that’s true for lots of people with whom I interact.”

Following that statement, Pompeo gave a wry smile, which one official close to the secretary of state told The Washington Post “spoke for itself.”

Meanwhile, Pompeo is poised to exert even more influence on foreign policy now that Bolton is gone. Pompeo met with Trump on Thursday to discuss the possibility of him even assuming the role of national security adviser on top of his current position. This would follow what one former administration official described as the "Kissinger model," in reference to when Henry Kissinger served in both roles under Presidents Richard Nixon and Gerald Ford.

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Trump, however, indicated afterward that this option is being ruled out. He told reporters Pompeo said he wants someone else "in there with him." Trump said a decision could come next week.

Several other names have already been floated to take over Bolton’s empty office, including U.S. Ambassador to Germany Ric Grenell, Special Representative for Iran Brian Hook, Special Representative for North Korea Steve Biegun and U.S. Ambassador to the Netherlands Pete Hoekstra.

Fox News' John Roberts contributed to this report.