The president and his advisers are seeking to harden immigration laws. In a call with reporters on Monday, senior White House officials said that Kirstjen Nielsen, the homeland security secretary, had attended over 100 meetings on ways to push forward.
But in the meantime, Mr. Judd, a 20-year veteran of the Border Patrol and leader of the estimated 18,000-member labor union, has caught Mr. Trump’s eye and earned the president’s praise for his television appearances.
Mr. Judd has reiterated the same talking points on Fox News, including urging Republicans to support Mr. Trump’s push for a border wall, ending the so-called catch-and-release practice and lauding the administration’s efforts on securing borders.
Mr. Trump, for his part, has a long habit of zeroing in on people who appeal to him on television. John R. Bolton, who was recently named Mr. Trump’s latest national security adviser, is a frequent Fox contributor, and Larry Kudlow, the president’s pick to head the National Economic Council, hails from CNBC.
Mr. Judd, of course, has not been elevated to the White House. But he has been publicly spotted in the president’s midst.
In an interview on Monday, Mr. Judd said he and the union came to Mr. Trump’s attention during the 2016 presidential campaign. After seeing Mr. Judd quoted in a news story, Mr. Trump reached out.
“Senator Ted Cruz quoted me from either a congressional hearing or a TV interview,” Mr. Judd said, “and immediately after, the Trump campaign reached out and strongly requested our endorsement.”
The National Border Patrol Council obliged in what was the first time the union had backed a presidential candidate. Mr. Judd said the primary reasons for the endorsement were rooted in Obama administration policies that he and other agents say impaired their ability to secure the border.
Of particular disdain was the catch-and-release policy. “We weren’t allowed to or given the resources to do our jobs,” Mr. Judd said. “So we decided to make our voices heard.”
The union’s frustrations found a sympathetic ear in Mr. Trump, who appointed Mr. Judd to his transition team. He was standing by as Mr. Trump signed an executive order, days after the inauguration, calling for the construction of a wall at the United States border with Mexico and the hiring of 5,000 additional Border Patrol agents.
In January, Mr. Trump publicly praised Mr. Judd’s continued support.
“Thank you to Brandon Judd of the National Border Patrol Council for your kind words on how well we are doing at the Border,” Mr. Trump tweeted after another Fox segment featuring Mr. Judd. “We will be bringing in more & more of your great folks and will build the desperately needed WALL!”
Among his fellow Border Patrol agents, however, opinions of Mr. Judd diverge.
Some rank-and-file agents call Mr. Judd a strong advocate for the force, including pushing for more personnel and better technology. Others say that Mr. Judd has, on occasion, taken positions that some agents call bizarre.
Last year, Agent Rogelio Martinez was killed while on patrol in Texas and his partner, Agent Stephen Garland, was seriously injured. Mr. Judd and other National Border Patrol Council officials have repeatedly said the two agents were the victims of a savage attack by smugglers or undocumented immigrants.
No evidence of smugglers was ever found in the area, and the Federal Bureau of Investigation said it was possible that the men were hurt accidentally. Oscar Carrillo, the local sheriff, helped investigate the case and concluded that the two men could have been hit by a vehicle.
Mr. Judd credits Mr. Trump for improving morale at the Border Patrol, which he said had been demoralized by the Obama administration. Mr. Judd has also used his relationship with the president to push for hiring the additional Border Patrol agents and for the reversal of several Obama-era policies. (The agents have not yet been hired.)
And Mr. Judd said he voiced his concerns to the Trump transition team about Mark Morgan, a former F.B.I. agent who was appointed chief of the Border Patrol late in the Obama administration. Mr. Trump ousted Mr. Morgan just days after assuming the presidency.
Mr. Judd is a Border Patrol agent stationed in Montana, where he has also forged ties with Senator Jon Tester, a Democrat. He was Mr. Tester’s guest to Mr. Trump’s State of the Union address in January.
“Brandon Judd has been on the front line securing our border and keeping Montanans safe,” Mr. Tester said in a statement at the time. “He is a Montana boy who climbed the ranks from an agent on our northern border to the very top of the National Border Patrol Council. Brandon’s input will play a critical role as we work toward a tough, bipartisan solution to a stronger border.”
The Border Patrol union had previously opposed building border walls and fences. In a mission statement on its website, the union said it did not believe in “wasting taxpayer money on building fences and walls along the border as a means of curtailing illegal entries into the United States.”
Still, Mr. Judd said, he never agreed with the statement and the union recently completed a survey of its members who “overwhelmingly say a wall system is necessary to securing the border.”
Mr. Trump is currently exploring ways to pay for the wall, including cutting proven methods for deterring migrants from crossing the border.