Homeland Security Secretary Markwayne Mullin has faced significant challenges in projecting an image of toughness on immigration, a key demand from President Trump's base, with his leadership standing undermined by White House disagreements.

Nearly six months into his tenure, Mr. Mullin has intensified his rhetoric and increased arrests and detentions, but influential conservatives continue to question his resolve on the issue, viewing him as too lenient.

The most recent setback for Secretary Mullin involved the White House's withdrawal of the nomination for Lance Schroyer, a senior adviser and ally, to lead Immigration and Customs Enforcement (ICE). This decision came less than three months after Mr. Trump publicly announced Mr. Schroyer's selection, leaving the agency without a confirmed director.

This move, without explanation from the White House, has fueled speculation about Mr. Mullin's influence and his ability to navigate the administration's internal dynamics. The nomination's failure has implications for the administration's immigration agenda and Mr. Mullin's standing within the department and the broader political landscape.

Sources familiar with the matter indicated that Tom Homan, Mr. Trump's border czar, was frustrated by Mr. Mullin's advocacy for Mr. Schroyer, whom Mr. Homan reportedly believed lacked the necessary experience for the ICE director role. Mr. Homan is known to favor the current acting ICE head, David Venturella, who has extensive experience within the agency.

Mark Morgan, who previously led U.S. Customs and Border Protection under Mr. Trump, suggested that Mr. Mullin's support for Mr. Schroyer, who also served on Mr. Mullin's security detail in the Senate, gave the impression of prioritizing personal connections over qualifications. Mr. Morgan commented that Mr. Mullin appears to be managing the department as if he were still a politician, a perception that could be detrimental to his effectiveness in his current role.

This is not the first instance of the White House overriding Mr. Mullin. Earlier this year, ICE paused nearly all traffic stops following an incident involving ICE officers in Maine. However, President Trump publicly announced that the stops would continue, reportedly displeased that Mr. Mullin had preempted the White House on the decision.

Mr. Mullin's public statements, such as his recent social media post trumpeting increased deportation flights, aim to project a hard-line stance. Yet, these efforts appear to be insufficient to overcome the doubts held by some within the administration and among conservative hard-liners, raising questions about his long-term effectiveness in shaping the administration's immigration policies.