Democrats Barack Obama and Hillary Clinton battled to a draw on "Super Tuesday" and John McCain took charge of the Republican race in coast-to-coast presidential nominating battles in 24 US states.
In their hard-fought Democratic duel, Obama won 13 states and Clinton took eight, ensuring a protracted battle for the nomination. Clinton's wins included the key prizes of California and New York on the biggest day of US presidential voting before the Nov. 4 election to succeed President George W. Bush.
"There is one thing on this February night that we do not need the final results to know: Our time has come," Obama, an Illinois senator, told cheering supporters in Chicago. "Our movement is real, and change is coming to America."
McCain won nine contests, including victories in California and the Northeast, to take a commanding lead in the Republican race. The Arizona senator whose campaign was all but dead last summer captured a huge haul of the convention delegates who select the party's presidential nominee, taking several big states where delegates are granted on a winner-take-all basis.
Republican rivals Mitt Romney and Mike Huckabee kept their hopes alive and vowed to fight on, but could face growing questions about the viability of their campaigns. Romney won seven states and Huckabee won five.
"Tonight, I think we must get used to the idea that we are the Republican Party front-runner for the nomination," McCain told supporters in Scottsdale, Arizona. "And I don't really mind it one bit."
RACE SET TO CONTINUE
The mixed results, with all contenders in both parties scoring at least five wins, appeared certain to prolong the hard-fought nominating races that began in early January. A new round of contests in a half-dozen states are scheduled within the next week.
The Clinton and Obama camps said they expected the night's delegate count to wind up relatively even. Overall, by the early hours of Wednesday, Clinton had 760 delegates and Obama 692, the Washington Post said, well short of the 2,025 needed to win the nomination.
The Democratic contest has given voters the chance to nominate a candidate who would be the first black US president, Obama, or the first female president, Clinton -- a New York senator and former first lady.
In the Republican race, the Post said McCain had 570 delegates to Romney's 251 and Huckabee's 175, with 1,191 needed to win.
McCain, who lost the Republican primary race in 2000 to George W. Bush, still faces a struggle to win over conservatives in the party, who have been unhappy with his views on immigration, tax cuts and campaign finance reform.
ECONOMY TOPS ISSUES
Economic worries -- plunging housing values, rising energy and food prices, jittery financial markets and new data showing a big contraction in the service sector -- eclipsed the Iraq war as voters' top concern in both parties, exit polls showed.
National exit polls showed more than half of Democratic voters ranked the ability to bring change as the top attribute for a candidate. Nearly one-quarter of Democrats voting in the party's 22 contests ranked experience, Clinton's selling card, as the most important attribute.
About 44 per cent of Republican voters preferred a candidate who shared their values, while one-quarter wanted a candidate with experience.
More than half the total delegates to the Democratic convention in August and about 40 per cent of the delegates to the Republican convention in September were up for grabs in Tuesday's voting.
But with no knock-out blows delivered, commentators pointed out that the continued nominating battles could mean more political mud-slinging and divisions within the parties.
"Since the voting did not produce dead-certain winners, the coming contests in states like Pennsylvania, Ohio, Texas, Louisiana, Washington and Virginia may only increase the pressure on campaigns that are more than willing to bare their fangs," the New York Times said in an editorial.
Obama scored victories in Alabama, Alaska, Colorado, Connecticut, Delaware, Georgia, Idaho, Kansas, Minnesota, Missouri, North Dakota, Utah and his home state of Illinois.
Clinton won Arizona, Arkansas, California, Massachusetts, New Jersey, Oklahoma, Tennessee and her home state of New York. She went into Super Tuesday battling a wave of momentum for Obama, who had surged in national polls on his message of change.
"I look forward to continuing our campaign and our debate about how to leave this country better off for the next generation," Clinton told supporters late on Tuesday.
Because Democrats distribute delegates in proportion to their vote statewide and in individual congressional districts, candidates can come away with large numbers of delegates even in states they lose.
Obama maintained his strong showing among black voters but also expanded support among whites, winning 40 per cent in Georgia, exit polls said. Clinton won heavy support from women and Hispanics, exit polls showed.
McCain won in Arizona, California, Connecticut, Delaware, Illinois, Missouri, New Jersey, New York and Oklahoma.
Huckabee, a Baptist preacher and former Arkansas governor, won in Alabama, Arkansas, Georgia, Tennessee and West Virginia.
Romney won in Alaska, Colorado, Minnesota, Montana, North Dakota and Massachusetts, where he served as governor, and Utah, which has a heavy concentration of Mormons. Romney would be the first Mormon president.
Huckabee's wins were fueled by strong support from evangelical Christians, and he split votes with Romney among conservatives unhappy with McCain. (Reuters)
Clinton, Obama draw; McCain leads in US vote