While coverage of the 2014 New Jersey Senate race thus far has centered on Newark Mayor Cory Booker and Sen. Frank R. Lautenberg, a third Democrat is laying groundwork to run as well: Rep. Frank Pallone Jr.

Pallone is all but certain to run for Senate if Lautenberg retires in 2014, according to knowledgeable sources.

The congressman, who has said little publicly about his next political move, is viewed as less likely to run if the 88-year-old Lautenberg decides to seek a sixth term. But he could find a three-way race with Lautenberg and Booker enticing.

“He has done the work all across the state, and not just in his district, to be a viable candidate and to be someone who would be taken seriously if he does decide to run for Senate,” one unaligned state Democratic operative said.

In a race against Booker, Pallone will have to leverage the New Jersey political machine to counter the mayor’s star power and national fundraising base.

All politics in the state is viewed through how the primary ballots are constructed. Each county party endorses a candidate, a recognition that is called “the line.” The candidate with the county party line receives preferential treatment on the ballot. It is nearly, but not always, impossible to win without picking up enough county lines.

“The line in New Jersey primaries is one of the foundations to winning an election,” one plugged-in Democratic operative said in an email.

Who gets what line will depend on whether Lautenberg decides to retire or run again — which is the question foremost on the minds of New Jersey political operatives.

Sometimes county endorsements are made by an individual county chairman, while other times it’s decided by committee. At least one New Jersey operative predicted the county chairmen will be inclined to give the line to Lautenberg if he seeks re-election, based on not wanting to establish a precedent that will encourage competitive primaries.

New Jersey is one of the most expensive states in which to run a statewide advertising campaign, so there is an added emphasis on grass-roots campaigning.

As of late November, Pallone had $3.5 million in his campaign account, and he has been making inroads with local Democratic Party officials for years in preparation for a statewide bid.

Geographically, his district is situated in central New Jersey. When it comes to politics, the state is sharply divided along geographic lines: North Jersey versus South Jersey. He is one of the few delegation members who registers in the local press of both regions.

For now, state Democrats insist their immediate goal is to find a candidate to take on popular GOP Gov. Chris Christie in November 2013. Christie is a possible 2016 presidential candidate. The Senate primary will more than likely occur in early June 2014, with the filing deadline sometime in April 2014.

“Our No. 1 concern is to get a gubernatorial candidate and lieutenant governor, to get that going,” Bergen County Democratic Chairman Lou Stellato said. “Who runs for Senate a year from November, that’s three lifetimes from now.”