A federal judge signaled that former National Labor Relations Board member Gwynne Wilcox will likely prevail in her legal challenge to President Donald Trump’s removal of her from the board.

Judge Beryl Howell appeared sharply critical of the Trump administration’s expansive view of the president’s power to ignore for-cause removal protections for officials like Wilcox during a Wednesday hearing at the US District Court for the District of Columbia.

The administration’s position—expressed during the hearing, and in a recent executive order and a statement from the acting solicitor general—looks like the “purest absolute power” to fire independent agency officials, said ...