Booker has long been seen as the favorite, but two independent polls released Monday show how large his initial advantage appears to be.
A Quinnipiac University poll found that Booker would get 53 percent of the vote in a Democratic primary, compared to just 10 percent for Holt, from central New Jersey, and 9 percent for Pallone of the Monmouth County Shore. A Rutgers-Eagleton poll had similar findings.
That leaves the congressmen with a lot of ground to cover and a short time to get there. Primary day is Aug. 13. The general election is Oct. 16.
Oliver was not included in either poll because it was only on Sunday night that she made clear her intentions to run.
The Republican primary is not expected to be competitive, given Lonegan's support from conservatives and Eck's inexperience.
For the Democrats, it's Booker "in a runaway in this first look," said Maurice Carroll, director of Quinnipiac's Polling Institute.
Just how hard a climb it will be for the congressmen was reflected in how few people know them statewide: 68 percent said they didn't know enough about Pallone to form an opinion, and 67 percent said the same thing about Holt, according to Quinnipiac. Rutgers' results were similar.
"We're not worrying about polls. Mayor Booker is focused on earning the votes of New Jerseyans," said Booker spokesman Kevin Griffis.
In an interview Sunday, Lonegan, from Bergen County, insisted he could beat any of the Democrats - despite what were seen as long odds against any GOP candidate.
"They're all the same, they're all just Obama supporters and Obama cronies," said Lonegan, the former head of the New Jersey chapter of Americans for Prosperity.
Lonegan, who fell short in the 2005 and 2009 Republican gubernatorial primaries but has won strong backing from conservatives, vowed to mobilize rural and suburban voters to win.
Monday's poll numbers come with a caveat: The odd August primary could be dominated by a small slice of voters.
Pallone and Holt are each banking on support from fervent liberals, while Booker has pitched a bipartisan appeal.
"I'm the progressive voice that New Jersey wants and needs," Holt said in an interview, calling himself more "battle-tested" than any other candidate.
Asked how he could catch Booker, Holt said, "My whole career and my accomplishments and my reputation have been built on hard work on substantive issues, not on celebrity, so this is something I'm good at."
Pallone has also cast himself as the champion of the left, fit to fill in for Lautenberg, a fierce liberal. He touted his support for the Affordable Care Act and suggested his policies were closer to core Democratic principles than Booker's.
"This campaign is going to be for the heart of the Democratic electorate," Pallone said at a Trenton news conference.
Oliver cited the importance of women running for higher office, noting that the entire New Jersey delegation is male.
"This is anybody's race to win," she told the Associated Press. "The challenge will be which of the candidates is best able to turn out their base."
Booker has already won support from two of the state's biggest political players: Essex County Executive Joe DiVincenzo, the top elected official in one of the state's most populous counties, and prominent Camden County Democrat George E. Norcross III, an owner of Interstate General Media, parent company of The Inquirer.
Eck, 62, is little known in political circles. Her appeal to supporters focused on the health law, saying "Obamacare ... will cause chaos and devastation."
The odd election timetable is a strange variable, but Christie rejected Democrats' claims Monday that having two major elections within weeks of one another - the Senate race in October and then the gubernatorial election in November - would prove costly and suppress voter interest.
"If candidates come out with a vision that excites the electorate, then people will turn out," Christie said. "If you run boring, visionless candidates, then people will go to the supermarket instead."
The Quinnipiac Poll surveyed 858 New Jersey voters with a margin of error of 3.4 percentage points. The poll included 306 Democrats with a margin of error of 5.6 percentage points.
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