The abrupt dismissal of Abigail Slater, the head of the Justice Department’s Antitrust Division, has sent fresh tremors through Washington, adding to a growing sense of instability inside an agency long regarded as the guardian of market competition and consumer protection.

Ms. Slater, a career antitrust lawyer who had led the division for less than a year, was removed from her post amid mounting tensions over high-stakes media and technology mergers. Her departure follows a series of personnel upheavals at the Justice Department, including the short-lived appointment of a U.S. attorney in the Northern District of New York who lasted just one day. Together, the moves have fueled concerns among legal experts and lawmakers that the department is entering a period of heightened political interference.

At the center of the dispute is a proposed consolidation involving major media assets, including CNN’s parent company, Warner Bros. Discovery. The outcome of that review carries enormous financial and political implications. Several bidders have expressed interest, including interests aligned with the Ellison family, whose business holdings include the technology giant Oracle and who are known to have close ties to President Trump.

Under federal law, mergers of this magnitude must be scrutinized by the Antitrust Division to determine whether they would substantially lessen competition or harm consumers. The division’s role is not to select winners, but to apply statutory standards rooted in the Sherman and Clayton Acts. That responsibility places its leadership in the crosshairs whenever corporate consolidation intersects with political power.

In recent months, President Trump publicly stated that he would not personally intervene in the review, saying the Justice Department would handle the matter. But critics note that the department’s leadership ultimately answers to the president, and they argue that replacing a career antitrust official during such a consequential review inevitably raises questions about independence.

Ms. Slater had built a reputation within the department for aggressively pursuing cases against dominant technology platforms. Under her tenure, the division continued litigation targeting Google’s digital advertising practices and maintained scrutiny of Apple’s App Store policies. Both companies have been frequent subjects of bipartisan antitrust concern, though their executives have also maintained visible relationships with political leaders of both parties.

Her removal has drawn criticism from Senator Elizabeth Warren, Democrat of Massachusetts, who characterized the decision as undermining the enforcement of competition laws. In a statement, Ms. Warren warned that weakening antitrust oversight would ultimately harm consumers through higher prices and reduced choice.

Former Justice Department officials, speaking on background to discuss internal deliberations, described Ms. Slater as a traditionalist in antitrust enforcement — skeptical of expansive corporate mergers and resistant to overt political pressure. They emphasized that career staff within the division are accustomed to operating under administrations of both parties, but rely on leadership committed to shielding enforcement decisions from political considerations.

The Justice Department has not publicly detailed the reasons for Ms. Slater’s dismissal. Attorney General Pam Bondi issued a brief statement thanking her for her service. A senior administration official, who requested anonymity to discuss personnel matters, said the president is “entitled to leadership aligned with his policy priorities.”

Those priorities appear to include a broader reshaping of the department. Over the past year, multiple U.S. attorneys have either resigned or been replaced after facing confirmation challenges in the Senate. Legal scholars say the cumulative effect risks eroding morale and institutional continuity within the nation’s principal law enforcement agency.

Antitrust enforcement has long oscillated between more permissive and more aggressive eras. In recent years, both Republican and Democratic administrations have signaled greater skepticism of large-scale consolidation, particularly in technology and media. But the current episode highlights how enforcement decisions can become entangled with political alliances, personal relationships and the strategic value of media ownership.

For consumers, the stakes are more prosaic but no less significant. When competition diminishes in telecommunications, digital advertising, entertainment or retail markets, economists generally find that prices rise and innovation slows. The Antitrust Division’s mandate is to prevent precisely those outcomes.

Whether Ms. Slater’s successor will maintain a similar enforcement posture remains uncertain. The pending media review, as well as ongoing cases against technology companies, will provide an early test of the division’s trajectory under new leadership.

For now, her dismissal underscores a broader tension confronting the Justice Department: how to preserve the credibility of independent law enforcement in an era when the boundary between politics and prosecution appears increasingly fragile.