WASHINGTON — Late last month, as members of Congress were poised to leave for their summer recess, the House Republicans’ top policy experts found themselves in a barren conference room in the Capitol’s basement, negotiating with the party’s most ardent opponents of immigration overhaul.

As senior members of the Judiciary Committee looked on, the opponents — Representatives Raúl R. Labrador of Idaho, Louie Gohmert of Texas, Steve King of Iowa and Mo Brooks of Alabama — reshaped two bills to address the rush of unaccompanied children trying to enter the country illegally. Representative Michele Bachmann, Republican of Minnesota, was there, too, and she and Mr. King later took to Twitter to post photos of themselves approving the final language.

For the Obama administration, which is considering carrying out broad immigration policy changes by executive decree, the end of the legislative session was potent evidence that Congress could not be a partner on the pressing, delicate policy decisions to come. A legislative year in which Speaker John A. Boehner of Ohio set out to publicly marginalize the more vocal right-wing members of his conference ended with them emboldened, and with new leaders ready to bring the right back into the fold.

“This was one of the most remarkable experiences I’ve had in my eight years in Congress,” Mrs. Bachmann said. “We were able to achieve unity across the conference in what is likely to be the most consequential issue of this time: immigration.”