Republican John McCain predicted he would get his party's nomination as Democrats Barack Obama and Hillary Clinton trade barbs on a hectic weekend before "Super Tuesday," the biggest-ever one-day White House nominating clash.
With 24 states voting Tuesday's showdown amounts to virtually a national primary. The day could be decisive for McCain in his bid to crush top Republican rival Mitt Romney, though neither the Clinton nor Obama campaigns believe the vote will decide the Democratic nominee.
McCain, 71, campaigning Saturday in traditionally conservative southern states, made a bold prediction about Super Tuesday.
"I assume I will get the nomination of our party," the Arizona senator told reporters, insisted he was not taking anything for granted. "I assume that unifying our party is a very critical item ... and I'm confident I can do that."
Meanwhile Clinton barnstormed through California, Arizona and New Mexico, and Obama visited Idaho and planned further rallies in Minnesota and Missouri, countering his rival's advantage in voter-rich states like California and New York.
Obama insisted he was the "underdog" as he tackles the Clinton election machine, despite wins in Iowa and South Carolina last month and a flurry of high profile endorsements.
"I don't think that there's any doubt that Senator Clinton -- she's still the favorite," Obama told reporters aboard his campaign plane. "When folks know me and my record, we do well. If they don't, she's got the advantages."
Obama, 46, on Sunday deploys talk show queen Oprah Winfrey and Caroline Kennedy, daughter of slain president John F. Kennedy, for a surrogate showdown with Bill Clinton in California, where the former president is popular.
Meanwhile Hillary Clinton, 60, reached out at her campaign stops to Hispanics, blue-collar workers and women, the core of her power base.
Her raspy voice, strained by countless stump appearances, struggled to be heard at times above the cheers as she thanked supporters gathered at California State University.
On her airplane with reporters Clinton likened Obama to the widely unpopular President George W. Bush, stating that her rival was an untested neophyte who would be a "leap of faith" for voters.
"We cannot afford to elect someone as we did with George Bush and then be somewhat surprised by the decisions that are made," she said.
Obama spokesman Robert Gibbs's reaction: "Sounds like the say anything, do anything of the Clinton campaign." Voters "want a break from that past, they want a different kind of future and they want real change," he said.
At a rally at a high school in Albuquerque, New Mexico, Clinton urged the audience to "hire me for the hardest job in the world."
"If you will stand with me in this primary, I will stand and fight with you throughout this election. They've (Republicans) been after me for 16 years and much to their dismay, I'm still here," she said.
McCain took his campaign to Tennessee and Georgia, where he cast himself as the only candidate who could beat the Democrats to the White House in November.
In a series of rallies McCain, a Vietnam war hero, appealed to conservatives by touting his 24 years of voting "to protect the life of the unborn," promised to only appoint conservative judges who "strictly interpret the constitution" and vowed to "never surrender" in the war on terror and to pursue Osama bin Laden to "the gates of hell."
McCain emerged as party front-runner after wins in South Carolina and Florida last week, sparking a furious backlash among social conservatives who have long opposed him.
Romney meanwhile spent much of Saturday at the funeral of Mormon church President Gordon Hinckley in Salt Lake City.
It meant losing a critical day of campaigning and highlighted his Mormon faith, which many evangelicals -- core Republican voters -- regard with suspicion.
But he was handed a victory in Maine's caucus late Saturday, which he celebrated as an endorsement of his "conservative vision for a stronger America."
Republicans Mike Huckabee and Ron Paul also held events, but are far behind McCain and Romney in the polls.
A Gallup daily tracking poll Saturday had Clinton up nationally by 48 percent to 41 against Obama, up from a three point lead on Friday. It gave McCain a 20 point lead over Romney.
"Super Tuesday" will see Democrats in 22 states and American Samoa vote on their presidential nominee, while Republicans will select their favorites in 21 states. In all, 19 states have hosting contests for both parties.
The states account for half the delegates to national party conventions in August and September which will formally anoint party nominees.