CONCORD - White House hopefuls fanned out across battleground states Sunday as the most intense US election in decades hit top gear awash in historic potential and millions of campaign dollars.
Though the 2008 race, set to be the first billion dollar election, has powered along at a relentless clip for eight months, the Labor Day weekend marks the traditional starting line, when voters start to tune in.
While Americans savored the last holiday weekend of summer, Democratic and Republican candidates cranked up the heat in crucial strategic states like Iowa, New Hampshire and South Carolina.
Brandishing new attacks on their rivals and poll-tested strategies, front-rank contenders and long-shot outsiders set off on the four-month sprint to state nominating contests which, one by one, produce party nominees for the November 2008 presidential election.
Hillary Clinton, leading Democrats in national opinion polls as she vies to become America's first woman president, took immediate aim at top rival, charismatic Senator Barack Obama.
The Republican race braced for a shake-up with the long-awaited official debut this week of screen star and former Tennessee senator Fred Thompson, in a late challenge to poll-topping former New York mayor Rudolph Giuliani.
Clinton on Sunday rolled out husband and ex-president Bill Clinton, still wildly popular among grass-roots Democrats, and a retooled speech for a "kick-off" swing through New Hampshire, a day before touring Iowa.
"There is a lot of the politics going on, and of course it will get more intense and heated in the next four months, but it really does make a difference who we elect," she said here.
Obama paints the Clintons and President George W. Bush as purveyors of a soiled brand of partisan politics, as he sets his sights on the former first lady in his quest to become America's first black president.
Battling the idea he is too inexperienced to guide the United States through a perilous age of terror, Obama will be hot on Clinton's heels with rallies in New Hampshire and Iowa this week.
John Edwards, the Democratic party's 2004 vice presidential nominee, meanwhile launched another campaign blitz in Iowa where he hopes to unleash a wave of momentum with calls for the United States to get out of Iraq.
"It's time for Congress to have some backbone and put an end to it," he said, in what appeared to be a veiled attack on Clinton and Obama, lawmakers criticized for failing to do more to end the war.
Thompson, gruff star of internationally syndicated "Law & Order," who hopes to emulate Ronald Reagan as a Republican actor who reached the White House, sits second in national polls.
Courting conservatives disappointed with their field, Thompson was due to hit Iowa, New Hampshire and South Carolina later in the week.
But by still not officially declaring his candidacy, has he left his run too late? Thompson's rivals have pounded the campaign trail for months, sucking up cash, endorsements and key party organisers.
Another Republican, former Massachusetts governor Mitt Romney, a multi-millionaire businessman credited with saving the 2002 Salt Lake City Winter Olympics from financial ruin, leads in Iowa and New Hampshire, where he was due to campaign on Monday.
The Labor Day before a US election year is always a milestone -- but in the intense 2008 race it has taken on even more significance.
Bids by large states like Florida and California to break the early voting monopoly of much smaller New Hampshire and Iowa have thrown campaign calculations into turmoil.
Top Democratic candidates have all signed on to a pledge to keep the sacred primaries order of Iowa, New Hampshire, Nevada and South Carolina intact.
But decisions by Republicans in South Carolina, traditionally the first southern state to vote, and Wyoming, to vault to the front of the pack, raise the possibility that Iowa, bound by state law to be the first state to open polls, might shift its mid-January date.
That unprecedented move could see the first votes in the 2008 election cast ... in 2007.
09/02/2007 19:54 GMT