ATLANTA — He says the United States is filling up with immigrants who do not respect the law or the American way of life. He refers to Latino groups as “the tribalists,” saying they seek to impose a divisive ethnic agenda. Of his many adversaries, he says: “The illegal alien lobby never changes. It’s the Wall Street wing of the Republican Party joining forces with the Chamber of Commerce, the far left and the Democrats in an effort to expand cheap labor and increase voting for the Democratic Party.”

D. A. King, who quit his job as an insurance agent a decade ago to wage a full-time campaign against illegal immigration in Georgia, is one reason this state rivals Arizona for the toughest legal crackdown in the country. With his Southern manners and seersucker jackets, he works the halls of the gold-domed statehouse, familiar to all, polite and uncompromising.

Now, like other local activists around the country, he is looking beyond Georgia to stop the House of Representatives from following the Senate and passing legislation that would open a path to legal status for illegal immigrants.

As lawmakers return to their home districts for the August recess, advocates like Mr. King are joining forces with national groups that oppose legalization and favor reduced immigration for an all-out populist push.

The zeal of militants like Mr. King is a problem for the House speaker, John A. Boehner of Ohio, and other Republican leaders, who are hoping to steer their divided caucus to pass a House version of legislation to fix the broken immigration system, which could include legal status for those who lack it — though probably not citizenship.

Mr. King says his wrath grew slowly, beginning in the 1990s with a feud with Mexican neighbors who disrupted the quiet of his leafy street. In Mr. King’s account, they parked fleets of run-down vehicles on their lawn and at one point housed 22 people in a jerry-built warren of rental rooms in the basement.

He took the neighbor to court over code violations, and the conflict boiled for seven years until the family moved away.

The mistrust of Mr. Boehner among Mr. King and his allies deepened recently when the speaker rebuked an anti-amnesty hero, Representative Steve King, Republican of Iowa, for commenting that young immigrants here illegally had “calves the size of cantaloupes” from running drugs across the border.

Mr. King in Georgia said he sided squarely with the congressman of the same name, although he might have chosen a milder metaphor. He nonetheless spared little in his description of Senator Marco Rubio, the Florida Republican who was one of the authors of the Senate bill, calling him a “smarmy and dishonest” turncoat. During the Senate debate, Mr. King designed and paid for thousands of bumper stickers as well as three large billboards along a commuter highway near Atlanta.

“Help us stop RubiObama amnesty!” one big sign read, with President Obama’s name joined by his hallmark red-white-and-blue letter to that of Senator Rubio.

His billboards instructed drivers to call a senator from Georgia, Johnny Isakson. Mr. Isakson, who supported a comprehensive bill in 2007, voted against the Senate legislation this year.

In Georgia, Mr. King has not been afraid to take on many adversaries, including the farmers and growers, business organizations, labor unions and Latinos. A big-shouldered former Marine, he often shows up with his own placards at rallies called by his opponents — just to let them know he is watching.

“I was taught that we have an American culture to which immigrants will assimilate,” Mr. King said. “And I am incredibly resentful that’s not what’s happening anymore.”