If you're a registered Democrat, you're a member of the Democratic Party. In NJ, you become a Democrat by filing a Party Affiliation form [pdf] with the County Superintendent/Board of Elections, or by voting in any Democratic Primary election (in June), if you have not already declared as a member of another party or Independent. You must register to vote 30 days before an election, and you can only file a party affiliation form after you are registered to vote. Note that if you register as an "Independent", you are barred from voting in primaries. If you are changing your party affiliation, or changing from Independent to a party, the change must be made 50 days before the primary in order to be eligible to vote. (See the Division of Elections Party Resources page for more information)

The Party is organized by County. Each municipality within a county is split up into voting districts. Voting districts are the smallest division and contain only a few hundred residents each. In the Primary Election of every even-numbered year (e.g. June 2006), Democratic voters in each voting district choose a County Committee Man and Woman to represent them in the County party organization. The County Committee people within each municipality select a Municipal Chair and Vice Chair. All the County Committee people within a particular county elect the County Chair and Vice Chair (often referred to as the party bosses).

Duties of County Committee people include nuts and bolts things like registering new voters, finding election board workers (e.g. competent people to run voting machines), serving as "challengers" on election day, GOTV (get-out-the-vote) and other campaign and election support.

They also serve as delegates to the annual County Convention (usually in March), where endorsement votes are held for County, State and National offices. Endorsement of local candidates is up to each municipal committee. Endorsed candidates get to run "in the column" with the Regular Democratic Organization on the Primary ballot. Other candidates are still free to run "outside the column" but face steep odds.

Many communities also have a voluntary Democratic "club", which any registered Democrat can join. These clubs vote to endorse candidates at all levels but have no statutory authority.