Some have knocked his ties to party leaders, but two of New Jersey's biggest power brokers are already with him: South Jersey's George Norcross, who is a managing partner of the company that owns The Inquirer, and Essex County's Joe DiVincenzo.
Weaknesses: The most common criticism is that Booker is too much of a lone star, too busy building up his name out of state and not tending to Newark and helping Democrats at home. Party insiders still gripe that he didn't run against Gov. Christie. Early on, some critics have also questioned how well his campaign was managed - especially given the waves he made by declaring his interest in running before the late Sen. Frank Lautenberg had a chance to announce his intentions.
Bottom Line: Booker begins the race as the heavy favorite. Anyone who hopes to catch him in just two months has a lot of work to do.
Strengths: He's been in the House for eight terms and is respected for his intelligence (he's a former Princeton nuclear physicist). Liberals and grassroots groups love him. His district includes Trenton and surrounding areas, and he's beloved by the unions representing state workers there, potentially giving him the help of a massive Democratic voting bloc.
Weaknesses: Holt is hardly known outside of his district, and he starts the race with only about $800,000 in cash on hand - about half of what Booker had after just three months of fund-raising. He and Frank Pallone might split the liberal and "anybody-but-Booker" vote.
Bottom Line: Holt fares about as well as Pallone in early polls from Quinnipiac and Rutgers-Eagleton, but he's got a lot less money. He and Pallone will have a hard time distinguishing themselves from each other. He'll need a huge push from labor and environmentalists.
Strengths: She is the Assembly speaker, so she has a higher profile than your average state lawmaker, and she's the only woman in the Democratic field. She stressed that distinction Monday, arguing for the importance of adding a woman to the state delegation, which is made up entirely of men. Oliver is from Essex County, home of Democrats' richest trove of voters, but then again, so is Booker, and the county's top official is with the mayor.
Weaknesses: Oliver was plucked out of obscurity when she became speaker in 2010, helped by the latest round of North-South horse trading. Despite her top legislative perch, she does not have a high profile in the state.
Bottom Line: Oliver stunned political observers by becoming speaker, so we should know not to underestimate her, but she also had a lot of help from the establishment when she did that. It doesn't appear that will be the case in this race.
Strengths: He's been stockpiling campaign money for this run for years, and starts with $3.7 million, the most in the field. He's also been a loyal Democrat, campaigning with the party's chosen candidates, spreading campaign cash around, and building ties with insiders. Liberal groups such as labor and environmentalists have long supported him and could play a big role in the primary.
Weaknesses: The average voter outside of his district hasn't heard of him. A Quinnipiac University poll found that 68 percent of voters don't know Pallone well enough to form an opinion of him. It will be hard to turn those voters into supporters in such a short time. As noted above, he and Holt will have a hard time distinguishing themselves from each other.
Bottom Line: Pallone passed up one opportunity to move to the Senate in 2002, and has long waited his turn for another shot. But he may have been overtaken by Booker, who has done things his own way and had success. Pallone will have to hope Democratic interest groups turn out in force on primary day, that liberals shy away from Booker's post-partisan message, and that they choose him instead of Holt.
Strengths: The only well-known Republican in the field and long the face of New Jersey's conservative movement, Lonegan has a fervent following that helped him win more than 40 percent of the vote against Christie in the 2009 gubernatorial primary. His fiery approach endears him to conservative activists and he can motivate his backers - as evidenced by the 7,210 signatures on his petition to run, even more than Booker's 7,162.
Weaknesses: His conservative message is great with his base, but so far he has not been able to sway enough of New Jersey's mostly liberal voters to actually win an election. He lost in the 2005 and 2009 gubernatorial primaries. New Jersey voters have regularly rejected even moderate Republicans running for U.S. Senate, so what will they make of the bomb-throwing Lonegan?
Bottom Line: With every other known Republican sitting out, Lonegan appears almost certain to finally get the chance to show his stuff against a Democrat in a statewide, general election.
He believes a true conservative - rather than a moderate - can win. But in New Jersey, where the state has leaned heavily Democratic on Senate and presidential elections, few analysts agree with him. The state hasn't voted a Republican into the Senate in more than 40 years.
Strengths: If Republicans are worried about having Lonegan as their standard-bearer, Eck is their only alternative. She's a doctor from Somerset County, in central New Jersey, and early on has focused on what she sees as the risks of Obamacare.
Weaknesses: She is almost entirely unknown. If she has been involved in electoral politics before now, no one has unearthed that history.
Contact Jonathan Tamari at firstname.lastname@example.org or @JonathanTamari on Twitter. Read his blog, "Capitol Inq," at www.inquirer.com/CapitolInq.