Outgoing Sen. Zell Miller — the Georgia Democrat who broke dramatically with his party by endorsing President Bush in the Republican National Convention’s keynote address — is joining the law and lobbying firm McKenna, Long & Aldridge, which was founded in Atlanta.

Miller will work in both the Atlanta and Washington offices on a range of government affairs issues, though he said in an interview Wednesday the he was unsure what his exact role at the firm will be.

“I have had a very limited conversation about what I would do,” said Miller, who said he is focusing on finishing a book. “They understand I’m going to be pretty involved in that.”

Eric Tanenblatt, who directs the firm’s government-affairs group, said he expects Miller to help expand the firm’s roster of defense-industry clients, which already includes Aventis Pasteur, GMH Military Housing, and Lockheed Martin.

The most noted line of Miller’s keynote address mocked Sen. John Kerry (D-Mass.), the Democratic presidential nominee, for voting against numerous weapons systems, asking whether Kerry wanted to leave American troops armed only with “spitballs.”

Miller will be moving back to his birthplace and longtime home in the mountains of north Georgia, traveling to Atlanta and Washington as the firm requests.

Given the one-year lobbying ban on former Members of Congress, Miller said he doesn’t expect to be “walking the halls of Congress.”

Miller said that he is unsure of how his partisan status would influence his abilities as a lobbyist.

“It’s always been one of my hallmarks to do business across party lines,” Miller said. “I was always successful in doing that until I got to Washington, where I kind of hit a brick wall.”

Though Miller says he will always remain a Democrat, he stopped caucusing with Democrats after the 2002 elections, then later wrote a book excoriating his national party and campaigned aggressively for President Bush.

Besides working on his new book, Miller said he wants to devote time to more “personal, spiritual and cultural things than I have before.”

Signing Miller marks a coup for McKenna, which has a modest but growing presence in Washington with a number of Georgia-based clients, including the Weather Channel, AFLAC, the University of Georgia, and Emory University.

Like Miller himself, McKenna’s roster of staffers straddles the political aisle.

The firm recently hired James Randolph Evans, who defended then-Speaker Newt Gingrich (R-Ga.) against ethics complaints, and Tanenblatt, the former chief of staff to Gov. Sonny Perdue (R-Ga.).

But Miller will also be reuniting with some Democrats from his past political life, including Keith Mason, Miller’s chief of staff when he was governor of Georgia, and Edgar Sims, who served as chairman of the Georgia Democratic Party under then-Gov. Miller.

Miller is the second Senator in as many days to announce a move to K Street.

Former Senate Majority Whip Don Nickles (R-Okla.) ended months of speculation about his post-retirement plans Tuesday when he announced he is forming his own shop, The Nickles Group.