McCain fell in Kansas to Mike Huckabee, who got nearly 60 percent of the caucus vote a few hours after telling conservatives in Washington, "I majored in miracles, and I still believe in them." The former Arkansas governor won all 36 delegates at stake.
Republicans also voted in a primary in Louisiana and held caucuses in Washington.
McCain began the day with 719 delegates, far ahead of his remaining rivals. Huckabee's Kansas victory left him with 234.
The Democratic race was far different, close and likely to get closer.
A total of 158 delegates was at stake in the Louisiana primary and caucuses in Nebraska and Washington. Caucuses in the Virgin Islands offered three more.
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 South Carolina, Alabama and Georgia.
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 of population in the hurricane-battered New Orleans area.
Clinton began the day with a slender delegate lead in The Associated Press count. She had 1,055 delegates to 998 for Obama. A total of 2,025 is required to win the nomination at the party convention in Denver.
The day's contests opened a new phase in the Democratic race between Clinton, attempting to become the first woman in the White House, and Obama, hoping to become the first black.
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 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.
People were turned away from a University of Maine student center Saturday morning as Clinton spoke to a capacity crowd of about 1,750 people. She urged supporters to participate in Sunday's caucuses.
"This is your chance to be part of helping Maine pick a president," she said. "So I hope even if you've never, ever caucused before, tomorrow will be your first time ... because there is so much at stake in this election."
Obama, also campaigning in Maine, looked ahead to the general election, criticizing Republican McCain without mentioning his Democratic rival.
McCain initially "stood up to George Bush and opposed his first cuts," Obama said at Nicky's Diner in Bangor. Now the GOP senator is calling for continuing those tax cuts, which grant significant breaks to high-income taxpayers, "in his rush to embrace the worst of the Bush legacy."
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.
