His winning margins were substantial, ranging from roughly two-thirds of the vote in Washington state and Nebraska to nearly 90 percent in the Virgin Islands. With returns counted from more than one-third of the Louisiana precincts, he was gaining 53 percent of the vote, to 39 percent for the former first lady.
As in his earlier Southern triumphs in Alabama, Georgia and South Carolina, Obama, a black man, rode a wave of African-American support to victory in Louisiana.
Clinton made no mention of the night's contests as she appeared at a Democratic Party dinner in Virginia, site of one of three primaries this Tuesday.
Instead, she criticized Arizona Sen. John McCain, the Republican nominee in all but name. "We have tried it President Bush's way," she said, "and now the Republicans have chosen more of the same."
She left quickly after her speech, departing before Obama's scheduled arrival. But his supporters made their presence known, as chants of "Obama" floated up from the audience as she made her way offstage.
In all, the Democrats scrapped for 161 delegates in the night's contests.
In initial allocations, Obama had won 31, Clinton nine.
In overall totals in The Associated Press count, Clinton had 1,064 delegates to 1,029 for Obama. A total of 2,025 is required to win the nomination at the national convention in Denver.
The Democratic race moved into a new, post-Super Tuesday phase as McCain flunked his first ballot test since becoming the Republican nominee-in-waiting. He lost Kansas caucuses to Mike Huckabee, gaining less than 24 percent of the vote.
Huckabee, the former Arkansas governor, got nearly 60 percent of the vote a few hours after telling conservatives in Washington, "I majored in miracles, and I still believe in them." He won all 36 delegates at stake.
Huckabee also edged ahead of McCain in caucuses in Washington, and in Louisiana's primary, where he was close to gaining 50 percent of the vote, the requirement for pocketing 20 delegates.
For all his brave talk, Huckabee was hopelessly behind in the delegate race. McCain had 719, compared with 234 for Huckabee and 14 for Texas Rep. Ron Paul. It takes 1,191 to win the nomination at the national convention.
The Democrats' race was as close as the Republicans' was not, a contest between Obama, hoping to become the first black president, and Clinton, campaigning to become the first female commander in chief.
The two rivals contest primaries on Tuesday in Maryland, Virginia and the District of Columbia, all states that Obama hoped to place in his column.
Preliminary results of a survey of voters leaving their polling places in Louisiana showed that nearly half of those casting ballots were black. As a group, African-Americans have overwhelmingly favored Obama in earlier primaries, helping him to wins in several Southern states.
Obama was gaining about 80 percent of the black votes statewide, while Clinton was winning 70 percent support among whites, the exit poll showed.
One in seven Democratic voters and about one in 10 Republicans said Hurricane Katrina had caused their families severe hardship from which they have not recovered. There was another indication of the impact the storm had on the state. Early results suggested that northern Louisiana accounted for a larger share of the electorate than in the past, presumably the result of the decline in population in the hurricane-battered New Orleans area.
McCain cleared his path to the party nomination earlier in the week with a string of Super Tuesday victories that drove former Massachusetts Gov. Mitt Romney from the race. He spent the rest of the week trying to reassure skeptical conservatives, at the same time party leaders quickly closed ranks behind him.
His Kansas defeat aside, McCain also suffered a symbolic defeat when Romney edged him out in a straw poll at the Conservative Political Action Conference meeting across town from the White House.
The day's contests opened a new phase in the Democratic race between Clinton and Obama.
The Feb. 5 Super Tuesday primaries and caucuses in 22 states, which once looked likely to effectively settle the race, instead produced a near-equal delegate split.
That left Obama and Clinton facing the likelihood of a grind-it-out competition lasting into spring - if not to the summer convention itself.
With the night's events, 29 of the 50 states have selected delegates.
Two more - Michigan and Florida - held renegade primaries and the Democratic National Committee has vowed not to seat any delegates chosen at either of them.
Maine, with 24 delegates, holds caucuses on Sunday. Maryland, Virginia and the District of Columbia and voting by Americans overseas are next, on Tuesday, with 175 combined.
Then follows a brief intermission, followed by a string of election nights, some crowded, some not.
The date of March 4 looms large, 370 delegates in primaries in Ohio, Texas, Rhode Island and Vermont.
Mississippi is alone in holding a primary one week later, with a relatively small 33 delegates at stake.
Puerto Rico anchors the Democratic calendar, with 55 delegates chosen in caucuses on June 7.
If Super Tuesday failed to settle the campaign, it produced a remarkable surge in fundraising.
Obama's aides announced he had raised more than $7 million on line in the two days that followed.
Clinton disclosed she had loaned her campaign $5 million late last month in an attempt to counter her rival's Super Tuesday television advertising. She raised more than $6 million in the two days after the busiest night in primary history.
The television ad wars continued unabated.
Obama has been airing commercials for more than a week in television markets serving every state that has a contest though Feb 19.
Clinton began airing ads midweek in Washington state, Maine and Nebraska, and added Maryland, Virginia and the District of Columbia on Friday.
The exit poll was conducted by Edison Media Research and Mitofsky International for The Associated Press and the television networks.
