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.