Overall, Clinton had 436 delegates to 352 for Obama, out of the 2,025 needed to secure victory at the party convention in Denver. Clinton's advantage is partly due to her lead among so-called superdelegates, members of Congress and other party leaders who are not selected in primaries and caucuses — and who are also free to change their minds.

Alabama and Georgia gave Obama three straight Southern triumphs. Like last month's win in South Carolina, they were powered by black votes.

Democrats and Republicans alike said the economy was their most important issue. Democrats said the war in Iraq ranked second and health care third. Republican primary voters said immigration was second most important after the economy, followed by the war in Iraq.

The survey was conducted in 16 states by Edison Media Research and Mitofsky International for The Associated Press and television networks.

Already, the campaigns were looking ahead to Feb. 9 contests in Louisiana, Nebraska and Washington state and Feb. 12 primaries in Maryland, Virginia and the District of Columbia. And increasingly, it looked like the Democrats' historic race between a woman and a black man would go into early spring, possibly longer.

The de facto national primary was the culmination of a relentless campaign that moved into overdrive during Christmas week.

After a brief rest for the holiday, the candidates flew back to Iowa on Dec. 26 for a final stretch of campaigning before the state's caucuses offered the first test of the election year. New Hampshire's traditional first-in-the-nation primary followed a few days later, then a seemingly endless series of campaign days interspersed by debates and a handful of primaries and caucuses.

Along the way, the poorest performers dropped out: Democratic Sens. Joe Biden and Chris Dodd, New Mexico Gov. Bill Richardson and Rep. Dennis Kucinich of Ohio; and Republican Reps. Duncan Hunter and Tom Tancredo, and former Tennessee Sen. Fred Thompson.

Former Sen. John Edwards pulled out of the Democratic race last week, and former New York Mayor Rudy Giuliani left the Republican field.

Edwards offered no endorsement as he exited, instead leaving Obama and Clinton to vie for help from his fundraisers and supporters.

But Obama benefited from an endorsement by Sen. Edward M. Kennedy, who made a series of campaign appearances in California as well as his home state of Massachusetts.

Giuliani quit the race and backed McCain in the same breath, clearing the way for the Westerner in New York and New Jersey.

Giuliani's departure also made it possible for California Gov. Arnold Schwarzenegger to back McCain. Schwarzenegger said he would not have done so as long as the former mayor was in the race.

Obama and Clinton spent an estimated $20 million combined to advertise on television in the Feb 5 states.

Obama spent $11 million, running ads in 18 of the 22 states with Democratic contests. Clinton ran ads in 17, for a total of $9 million.