( dpa ) - Former first lady Hillary Clinton took an early lead over Democratic rival Barack Obama in the Super Tuesday presidential primaries, while John McCain picked up support that could help him seal the Republican Party nomination.
With a record 24 states holding votes coast to coast, Clinton took an initial six, including New York and New Jersey, projections by US television networks based on exit polls showed. Obama, seeking to become the first African-American president, was forecast to win Illinois, which includes his home town of Chicago, and three others.
Vietnam war veteran McCain, 71, pulled ahead of millionaire businessman Mitt Romney and Arkansas governor Mike Huckabee, 52, a Baptist pastor with a strong appeal among social conservatives who won the day's first contest in West Virginia.
On the biggest-ever single day of presidential preference votes by the two major parties, the top prizes included California, New York, Illinois and New Jersey. Both parties were choosing about half their delegates to nominating conventions in the summer.
With excitement and suspense rivalling that of a general election, many voters weighed their choice up until the moment they entered the polling booth.
Heavily tatooed artist Chuck Martin, 27, was still undecided between Clinton and Obama, both US senators, who went into Super Tuesday running neck-and-neck for the Democratic nomination and the chance to retake the White House for their party.
"This is the first time I've ever bothered to vote, and man, I'm having a hard time," Martin said. "Clinton and Obama are both such good candidates."
Because Democrats award delegates mostly according to a contender's share of the vote in each state, Tuesday could end with Obama, 46, and Clinton, 60, still locked in battle for the centre-left party's nomination.
National polls showed Obama gaining momentum ahead of Tuesday's vote, bolstered by backing from fellow senator Edward Kennedy and Caroline Kennedy, brother and daughter of slain president John F Kennedy - both icons of the left.
Obama was in a statistical tie with Clinton, including in some polls in delegate-rich California. California's time zone means it will be among the last states to announce results.
McCain, a US senator from Arizona, has surged to the lead in the Republican field. He won key endorsements by California Governor Arnold Schwarzenegger, the New York Times and the Los Angeles Times.
McCain said Tuesday could be a big day for his campaign, but when pressed in a television interview, he refused to get too far ahead of himself and predict a final victory.
"It's well-known, I'm very superstitious," he said on NBC. "And so I carry around my penny that I found with the head up."
Republican Party rules that give the first-place finisher the entire delegation in a handful of winner-take-all states could help him nail down the nomination Tuesday, though his two major rivals could also splinter the vote.
Obama, son of a Kenyan father and a white American mother, has emerged as perhaps the most exciting new face in the 2008 race.
He and Clinton have battled for weeks as both camps sharpened the contrast between Obama's lofty message of change - a powerful vote-getter in a nation weary of Bush and the Iraq war - and Clinton's greater political experience she brings to the White House on "day one."
Yet the Democratic nominee is far from assured of victory in the November 4 presidential election. In the critical battle for independent voters, polls suggest McCain would be a strong match for Clinton or Obama.