Democrat Hillary Clinton resurrected her White House campaign with stunning primary victories over Barack Obama in Ohio and Texas, but the longest and costliest nominating race in history is far from run.
With a Democratic nominee perhaps months away from being anointed, Senator John McCain moved into general-election mode after capturing the Republican mantle by winning all four contests held on "Super Tuesday II."
Clinton took Ohio, Texas and Rhode Island while Obama had only the consolation prize of Vermont, on a night of high drama that rescued the former first lady's campaign from the threat of oblivion.
"I am thrilled at this vote of confidence from the people of the great state of Texas, a state I know and love," Clinton, 60, said after the Lone Star state's primary became her final scalp of the night.
"Tonight we won three out of four contests and began a new chapter in this historic campaign," she said, after earlier vowing at a rally in Ohio that "we're going all the way" to the White House.
But Obama stressed that the New York senator still faces tough odds to overhaul his lead among the Democratic delegates who will choose the party's presidential candidate for the November election.
And following its day-long primary, Texas convened Democratic caucuses that were to award one-third of the state's total delegates. The Clinton campaign hurled allegations of caucus dirty tricks at the Obama camp.
"No matter what happens tonight, we have nearly the same delegate lead as we did this morning, and we are on our way to winning this nomination," Obama, 46, told an outdoors rally in balmy San Antonio, Texas.
The Illinois senator bidding to be America's first black commander-in-chief said both Clinton and McCain had attacked his mantra of change and hope as "eloquent but empty."
But he said: "It is now my hope and our task to set this country on a course that will keep this promise alive in the 21st century. And the eyes of the world are watching to see if we can."
In the battle for psychological momentum, Clinton earned bragging rights with her victories in Texas and Ohio to add to her triumphs in other big states such as California, New York and New Jersey.
"I think what's noteworthy is a lot of pundits thought we were coming tonight to a funeral for Hillary Clinton," said Paul Begala, a former aide to president Bill Clinton.
"Instead we saw a resurrection."
But with Democratic primaries awarding their delegates on a proportional basis, Obama's lead of about 100 delegates, after 11 nominating wins in a row in February, looked intact.
Neither Obama nor Clinton is near the winning line of 2,025 candidates, leaving the prospect of a months-long battle through Pennsylvania on April 22 and maybe all the way to the Democratic convention in August.
With nearly all Ohio precincts reporting their results, Clinton enjoyed a commanding lead over Obama of 55 percent to 43. In the Texas primary, Clinton led 51-47 with more than four-fifths of districts reporting.
McCain, 71, too capped an amazing comeback after his campaign had looked dead and buried in mid-2007, crippled by overspending and infighting that led to an exodus by top aides.
But now, McCain can enjoy laying out his lines of attack for the November election while watching the Democrats fight tooth and nail.
The Arizona senator promised to combat Islamic extremism, keep the US economy open to world trade and lower taxes if elected the successor to George W. Bush, whose blessing he was to receive at the White House on Wednesday.
"And I am very pleased to note that tonight, my friends, we have won enough delegates to claim with confidence, humility and a sense of great responsibility that I will be the Republican nominee for president of the United States," he told cheering supporters in a Dallas hotel.
His victories Tuesday took McCain, a Vietnam war hero distrusted by many conservatives for his maverick stance on issues such as immigration, over the Republican finish line of 1,191 delegates.
His last remaining challenger, former Arkansas governor Mike Huckabee, bowed out and pledged fealty to the Republicans' new standard-bearer.