Steve Kornacki: The geographic dividing lines shaping New Jersey's primary

Rep. Mikie Sherrill heads into Tuesday’s primary as the favorite to win the Democratic nomination for governor of New Jersey.

Rep. Mikie Sherrill heads into Tuesday’s primary as the favorite to win the Democratic nomination for governor of New Jersey. She has blanketed the pricey New York and Philadelphia metro airwaves with television ads, she enjoys the backing of much of the party’s establishment, and she had opened double-digit leads in two polls that were released several weeks ago.

There is uncertainty, though. Credible public polling has, overall, been limited and infrequent. And court-imposed changes to the layout of the primary ballot could dramatically dilute the power of the endorsements Sherrill has received from key county Democratic organizations.

Sherrill’s opponents have each made inroads. But, at least so far, that seems to have had the effect of keeping them in one another’s way, preventing one from emerging as the clear alternative to Sherrill. Consider the state’s political geography.

You can draw a line south of Mercer and Monmouth counties, roughly where Route 195 would be on a map. Below that is South Jersey. Democratic politics here are dominated by an old-fashioned political machine that is backing the lone South Jersey candidate in the field: former state Sen. Steve Sweeney.

The trouble for Sweeney is that only about 30% of all primary votes will come from tis region. And because South Jersey is part of the Philadelphia media market, he’s not well-known in the rest of the state, which is served heavily by the New York market.