The extraordinary battle for the White House continued today, with a full recount coming in Florida to determine whether Texas Gov. George W. Bush or Vice President Gore becomes the next president.

Gore had called Bush early today to concede the election. But in a move surely unprecedented in U.S. history, he later called back to retract it, as returns showed Florida agonizingly close.

If Bush wins Florida and therefore the election, as his campaign predicts, it will mark the first time since 1888 that a candidate won the popular vote but not the all-important Electoral College vote. Gore was ahead in the nationwide popular tally by well over 200,000 votes this morning, a lead that no recount appears capable of overturning.

Lawyers and advisers for the two nominees raced to Florida this morning to investigate two potentially crucial situations. In one, Democrats claim that more than 3,000 Gore votes in Palm Beach County may have been mistakenly recorded as votes for third-party candidate Patrick Buchanan because of oversized ballots whose lines were skewed.

In the other, an unknown number of absentee ballots have yet to be tallied. Some state officials said a recount could be completed by late Thursday, but absentee ballots mailed from overseas have 10 days to arrive. They must have been postmarked by yesterday to be valid. About 1,000 Florida voters live in Israel and many can be expected to have supported the Democratic ticket.

As of mid-morning, the Florida tally showed Bush leading by fewer than 2,000 votes. That includes all votes cast yesterday at polling stations, all domestic absentee ballots and all foreign absentee ballots received by 7 p.m. yesterday.

Bush campaign chairman Don Evans said he believes the governor has won the election, but Gore's chairman, William Daley, said it's too close to call. He said former secretary of state Warren Christopher will monitor the recount for Democrats. Florida law requires an automatic recount if the margin of difference is less than one-half of 1 percent, as this one clearly is.

In Congress, meanwhile, Republicans appear likely to cling to the slimmest of majorities. They hold a 50 to 49 edge over Democrats in the Senate, with one race too close to call. In the House, Democrats have picked up at least one seat, and possibly two more. Currently, the GOP holds the Senate by 54 seats to 46 and the House by 223 seats to 210 (plus the two independents).

With most of the presidential votes tallied in Oregon this morning, Bush held a modest lead, while Gore apparently carried Wisconsin by a tiny margin. But Florida, with its 25 electoral votes, is the only state that matters now, as the nominee who carries it will win the election.

Should Bush prevail, some Democrats doubtlessly will point a finger of blame at Green Party nominee Ralph Nader. Nader, who drew more support away from Gore than from Bush, won enough votes in Florida, Oregon and New Hampshire to prevent the vice president from winning those states with clear margins.

Nader failed, however, in his goal of capturing 5 percent of the nationwide vote, which would have entitled his Green Party to federal campaign funds in 2004.

Nader was unapologetic in a news conference today. Gore, he said, "should have land-slided George W. Bush. . . . The Democratic Party must face the facts that it has abandoned its progressive roots." If Gore wins the White House, Nader said, "he will have ample time to demonstrate that relying on Al Gore is a risky proposition."

The two presidential candidates rode an emotional roller coaster as they watched the unfolding drama in the states from their headquarters in Austin and Nashville, sparked by a premature call by the networks that put Florida into Gore's column early Tuesday evening--only to be retracted later. Shortly before 2:30 a.m. today, the networks and other news organizations awarded the state and the presidency to Bush. But within an hour the election was once again thrown into doubt.

Daley appeared before Gore supporters in pouring rain in Nashville to say the election was not over. "I've been in politics a very long time but I don't think there's ever been a night like this one," he said.

Bush campaign spokesman Ari Fleischer said in morning television shows that the governor is "confident." He told ABC News: "I think we've gone into extra innings but we're still about to win this contest."

A full recount of Florida's vote may not be complete for 10 days, although it's possible the outcome can be determined before then. Absentee ballots dispatched domestically must arrive by 7 p.m. on Election Day. But voters overseas get a 10-day extension, so long as their envelopes are postmarked by Election Day.

In 1996, about 2,300 Florida ballots arrived from overseas within the 10-day window. But state officials have no way of knowing how many to expect this year.

Florida is an attractive state of residence for expatriate Americans because it has no income tax. In addition, Florida is home to several military units frequently deployed abroad. But the only one with thousands of potential voters--the aircraft carrier USS John F. Kennedy, with a crew of 5,000--is at its dock in Mayport, Fla.

A separate voting problem in yesterday's election could complicate the pending recount. In Palm Beach County, a different ballot was used in some precincts, apparently confusing some pro-Gore voters who may have inadvertently voted for Reform candidate Patrick J. Buchanan.

"One supervisor of elections decided to do their ballot a little bit differently than others," Florida Attorney General Bob Butterworth told NBC's "Today" show.

Butterworth said that if Buchanan won a disproportionate percentage of votes in Palm Beach County, "that may be a problem." In fact, Buchanan appears to have done better in Palm Beach, which is heavily Democratic, than in comparable areas. He won 3,407 votes there, but got only 789 in Broward County, which lies immediately to the south, and 108 in Martin County, which is immediately to the north of Palm Beach. Hillsborough County, which tends to be conservative, gave Buchanan 800 votes.

Florida's mandatory vote recount is being supervised by the Election Canvassing Commission, which is responsible for certifying the results of any election for federal or statewide office. The commission is made up of Gov. Jeb Bush (the GOP presidential nominee's brother), Secretary of State Katherine Harris and the director of the Division of Elections, Clay Roberts.

County canvassing boards that conducted yesterday's original count will also conduct the recount. The boards are typically made up of a county judge, the chair of the board of county commissioners and the county supervisor of elections.

In advance of the recount, state law requires the county canvassing board to test all tabulating equipment. The next step is to check the Election Day counts sent by precinct election boards to the county authorities against the mechanical or electric counters on individual voting machines. The county board then has the authority to conduct a manual recount.

If any precinct recount "indicates an error in the vote tabulation which could affect the outcome of the election," state law allows the county board several options. It can correct the error and recount the rest of the county again with regular tabulation computers. It can ask state electoral authorities to verify the tabulation system's accuracy. Or it can conduct another manual recount. That count must be open to the public and conducted by teams of two electors, one from each major party. Whatever the ultimate result of Florida's recount, some people doubtlessly will be skeptical. Not only are the Florida and Texas governors brothers, but another key player, Butterworth, is a Democrat who chairs the Gore campaign in Florida.

The state also has some history of voter irregularities. A judge two years ago threw out the results of Miami's 1997 municipal election because of voter fraud. That case turned on absentee ballots. In a civil lawsuit, the Miami-Dade County supervisor of elections testified that absentee ballots usually account for about 5 percent of all vote, but they totaled 11 percent in the 1997 mayoral contest. In Miami's Little Havana district, where many of the fraud claims surfaced, absentee ballots accounted for nearly 20 percent of the total.

A state court subsequently threw out all 5,000 absentee ballots cast in that election. A federal judge upheld that decision by dismissing a class action suit by absentee voters who claimed their constitutional rights were violated.

In another Florida contest involving recounts and absentee ballots, Democrat Buddy MacKay was declared the winner on election night in the state's 1988 U.S. Senate race. But when the absentee votes were counted, Republican Connie Mack was found to have won.

The seesaw battle guaranteed that whoever claims the White House will face an enormous challenge in trying to unite a country that appeared sharply divided last night and with the House and Senate closely split between the two major parties.

First lady Hillary Rodham Clinton made history by winning her bid to claim a Senate seat in New York by easily defeating Rep. Rick Lazio (R). In Virginia, Sen. Charles S. Robb (D) lost his bid for reelection, falling to former governor George Allen (R).

Democrats, who needed a net of five seats to take control of the Senate, picked up GOP-held seats in Florida, Minnesota, Delaware and Missouri, where the late Mel Carnahan (D) defeated incumbent Sen. John D. Ashcroft (R). That clears the way for his widow, Jean, to be appointed to the seat in one of the most bizarre contests of a suspense-filled election year. In addition to Virginia, Republicans picked up a Democratic-held seat in Nevada, as expected.

Many of the states Bush won were reliably Republican states, but his decision to try to enlarge the electoral map by challenging Gore in traditional Democratic areas paid dividends. His victory in the vice president's home state of Tennessee was a psychological blow to the Gore campaign. President Clinton carried Tennessee in 1992 and 1996.

But after midnight, it was Florida causing all the havoc. The all-night confusion triggered surreal scenes in Austin and Nashville, where Bush and Gore, respectively, hunkered down with family and supporters.

In Nashville, Gore went to the War Memorial apparently planning to tell his backers he had lost. But Florida tallies showed him closing the gap, so he retreated to a holding room. There, he called Bush at about 4 a.m. to say the race was still on.

Then, as Daley read a statement to the rain-soaked crowd, the vice president raced away in a car and small motorcade, leaving reporters and others behind.

When journalists caught up with the Gore entourage at the Lowe's Hotel, sleep-deprived aides wandered through the lounge and bar, swapping information about the bizarre events in Florida. Ron Klain, a lawyer and former Gore chief of staff, hurried from the Lowe's around 5 a.m., saying he would catch a 7 a.m. charter flight to Tallahassee to help oversee Florida's recount.

Staff writers Ceci Connolly, Tom Ricks, Roberto Suro and Ben White contributed to this report.