Sen. Zell Miller, the colorful, cantankerous and conservative Georgia Democrat, announced yesterday that he will not seek reelection in 2004 and won't campaign to help his party hold the seat.

His decision surprised and perplexed Democrats reeling from the pounding they took in Georgia in November. Republican challengers easily defeated two seemingly popular incumbents, Sen. Max Cleland and Gov. Roy Barnes. If anyone could stem that tide in the next election, it might have been Miller, whose two terms as governor in the 1990s made him one of the most popular figures in the state.

Instead, prominent Republicans are salivating over the seat, and the prospects of Democrats regaining the majority in 2004 are a bit dimmer.

Miller, who turns 71 next month, entered the Senate in July 2000 after the death of Sen. Paul Coverdell (R). Four months later, he was easily elected to serve the four years remaining in Coverdell's term.

He promised to ignore party lines, and that's what he did. Miller has broken often with Democratic leaders to support programs pushed by President Bush. He backed the Bush tax cuts of 2001, and yesterday, his press secretary, Joan Kirchner, said "he is inclined to support" the Bush plan for more tax cuts. "He believes Congress should try to pass the largest tax cut that reaches the most people the fastest," she said.

Miller frequently heaped scorn on Democratic Party Chairman Terence R. McAuliffe, saying that McAuliffe was out of touch with voters and pushing the party too far to the left. "The strength of our party has always been our big tent," Miller wrote in a 2001 letter to The Washington Post. "But lately our chairman seems to be shrinking that tent to the size of one of those snow-cone cups turned upside down. Well, maybe a little bigger than that, say, a dunce cap."

That sort of language was typical of the senator, who prides himself on his knowledge of country music and his passion for pickup trucks.

"I realize some will call me a 'lame duck,' " Miller said in a statement. "But those who know me know I will be the 'same duck,' continuing to serve no single party but all the people of Georgia."

Miller's announcement hit Georgia Democrats out of the blue. State party chairman Calvin Smyre said he spent time with the senator Tuesday and got nary a hint. "We're surprised and disappointed," he said. "It would've been outstanding to have him on the ticket in 2004."

Party leaders will begin talking about a successor at a meeting Saturday, Smyre said, noting that the early decision to retire creates a "window of opportunity" for a candidate to put together a strong campaign.

But some Georgia Republicans believed Miller's timing favored their party because as long as he was potentially in the race, Republicans would be running uphill. The fact that Miller would not help the eventual Democratic nominee -- "I will neither endorse nor campaign for any candidate seeking this seat," he said -- added further to the sense that the biggest impediment to the GOP in Georgia was stepping out of its way.

At least four Republican House members -- Reps. Charles Whitlow Norwood Jr., Mac Collins, Jack Kingston and Johnny Isakson -- are considering the race. All have formidable campaign accounts and fundraising networks.

Democrats will be hoping for a bruising Republican primary to offset that advantage; the White House and state GOP Chairman Ralph Reed are likely to rally behind one candidate. At least one Republican weighing the race, former representative Robert L. Barr Jr., has been willing to clash with the party's establishment in a primary.