When Speaker Mike Johnson and scores of House Republicans converged in Eagle Pass, Texas, on Wednesday to call for a crackdown on migrants at the border, they had a somewhat unlikely host.

It was only months ago that Representative Tony Gonzales, the Texas Republican who represents the busy border crossing and the majority-Hispanic district that surrounds it, broke with his party in opposition to parts of its hard-line approach on immigration. Back then, he warned his colleagues against an overly draconian approach and urged them not to politicize the issue.

Now Mr. Gonzales, who has faced a constituent backlash and multiple primary opponents in his competitive district, has swung into line with the zeal of a convert, becoming a chief champion of Republicans’ strict border enforcement bill and a proponent of efforts to use it as political leverage against President Biden.

He has endorsed calls to make border security improvements a precondition of securing military aid for Ukraine and keeping the federal government open. And he has been working closely with Mr. Johnson to maintain pressure on the rest of Congress to embrace the House G.O.P.’s hard line.

It is hardly surprising that Mr. Gonzales, a second-term congressman in a swing district, would play an active role in immigration policy debates. His congressional district, Texas’ 23rd, includes the longest stretch of the U.S.-Mexico border and contains the entirety of the Del Rio sector along the Rio Grande, which consistently ranks among the busiest for Border Patrol encounters with migrants attempting unlawful entry.

In his few years in office, Mr. Gonzales has hosted several delegations of lawmakers for fact-finding trips along his stretch of the border, including two speakers and several of the senators now scrambling to strike a bipartisan deal to clamp down on migrant crossings. Republicans have demanded such measures in exchange for supporting a bill to speed fresh military assistance to Ukraine for its war against Russian aggression.

But Mr. Gonzales’s swift shift from skeptic to champion of House Republicans’ hard-line immigration bill illustrates the political potency of the issue within the G.O.P., and how little room there is for dissent on a topic that has galvanized the party’s far-right base.

“We are united in making sure House Republicans’ top priority is securing this border,” Mr. Gonzales told reporters on Wednesday during a news conference in Eagle Pass, standing with more than 60 of his Republican colleagues on a bank of the Rio Grande.

Mr. Gonzales has said he and Mr. Johnson confer weekly about the state of the border and Senate negotiations to strike a bipartisan border security deal. Mr. Johnson has repeatedly warned Mr. Biden and Democrats that he will not tolerate anything less than the severely restrictive bill the House passed last spring.

But unlike Mr. Johnson and some of his far-right colleagues, Mr. Gonzales has hinted at openness to a compromise.

“Now is the time to make sure America is safe, and we do that by taking a down payment on border security in ’24,” he told reporters on Wednesday, adding that Republicans could “come back for the rest when we win back the White House in ’25.”

Mr. Gonzales declined through a spokeswoman to be interviewed on Wednesday. But he said this week that if senators could strike a bipartisan border deal that could draw the supermajority needed to advance in the Senate, it would be difficult for House Republicans to reject it out of hand even if it fell short of what they were demanding.

“If the Senate can get to 60 in a meaningful way, that would send a powerful message that the House couldn’t just set aside,” Mr. Gonzales told CNN on Tuesday. “But to be very clear, there has to be meaningful border solutions. It can’t just be window dressing.”

A year ago, Mr. Gonzales was unabashedly critical of legislation written by Representative Chip Roy, also a Texas Republican, to hold asylum seekers in detention facilities while their cases were pending in immigration court and expand the administration’s ability to deport migrants once detention beds were full.

Mr. Gonzales criticized the bill as “anti-American” and “not Christian,” drawing a censure from the Texas Republican Party, which also rebuked him for supporting gun safety measures and defending same-sex marriage. Still, Mr. Gonzales continued to object, threatening to rally Hispanic Republicans against the measure and eventually forcing House G.O.P. leaders — who needed their votes to push the bill through the narrowly divided chamber — to pare back the restrictions.

The bill, which Mr. Gonzales ultimately supported, still mandated severe limits on asylum, reducing the categories of migrants eligible to make claims, requiring migrants to be held in Mexico while awaiting their court dates and expanding the administration’s power to swiftly remove migrants before they could make a case to stay. Those proposals have emerged as sticking points in the Senate negotiations, which have also involved discussions about limiting entry to the country when detention facilities reach capacity.

Mr. Gonzales continues to speak favorably about legal immigration, and support the idea of political compromise. But in the months since the House vote, border crossings have increased, encounters with migrants along the Texas stretch of the border have climbed and Mr. Gonzales has drawn primary challenges from three other Republicans. Now he has become a booster for the G.O.P.’s approach to border security, and a more impassioned voice for getting tough on the Biden administration.

Mr. Gonzales has shifted to the right on other border-related matters. He has teamed with Representative Majorie Taylor Greene, the hard-right Georgia Republican, to promote a resolution to impeach Alejandro Mayorkas, the homeland security secretary, for carrying out policies that the G.O.P. has blamed for driving up unlawful migrant crossings and fentanyl deaths in the United States.

Though the resolution did not get through the House, the Homeland Security Committee is expected to begin impeachment hearings on Mr. Mayorkas next week.

In recent days, Mr. Gonzales has also endorsed calls promoted by the ultraconservative House Freedom Caucus to make substantial border security changes a precondition of funding the federal government.

“Unless there are meaningful border solutions in there,” he said on “Fox News Sunday,” “you can count me as a no.”