The New Jersey primary is Tuesday. Here’s what you need to know.

New Jersey is holding its primary election Tuesday. But like other states that expanded the use of mail ballots amid the coronavirus pandemic, most of the voting has likely already happened.

The state pushed back its primary from June 2 and Gov. Phil Murphy ordered the election to be conducted mostly by mail. Most voters were automatically sent a mail ballot, with some others receiving an application for one.

With the Democratic presidential race long since effectively decided, there are only a couple House races in South Jersey we’re watching.

Here’s what you need to know.

A little more than a month after Pennsylvania ran its first statewide election of the coronavirus era, it’s New Jersey’s turn. And as in Pennsylvania last month, the process of voting will be quite different.

Polls will still be open on a limited basis from 6 a.m. to 8 p.m. — at about 1,600 locations or so across the state, slightly less than half of the normal 3,400 locations. Those are mostly for people with disabilities, people without permanent housing, and others who prefer to vote in person.

But most votes are being cast by mail. And lessons learned from that will help elections officials figure out how to handle the high-turnout presidential election in less than four months. For example, voters will be given a chance to fix problems with their signatures, such as ballots that are missing signatures, following problems with an all-mail municipal election in May.

One lesson that’s already clear: Counting votes will take time. As in Pennsylvania, results could take days or even weeks to become clear, with every vote cast either by mail or by paper ballot at the polls. Paper ballots take longer to count than votes cast on machines at polling places, and mail ballots won’t begin getting counted until Tuesday.

Votes will also keep coming in, with any mail ballot postmarked by Tuesday counted if it arrives within a week.

Strategists in both parties are closely watching the primaries in two South Jersey districts that voted for Barack Obama twice before flipping to Donald Trump in 2016.

Democrats won both seats in 2018, helping deliver the party its House majority. But by the end of last year, New Jersey’s 2nd District captured national attention when first-term Democratic Rep. Jeff Van Drew announced he was switching parties after outraging Democrats by opposing Trump’s impeachment.

Trump held a Wildwood rally to reward Van Drew for his defection, and Trump allies largely cleared the GOP primary field for their new ally.

Van Drew is now the heavy favorite in the Republican primary against Bob Patterson, a former speechwriter in the George W. Bush administration who ran unsuccessfully for Congress in 2016 in a different district.

Running in the Democratic primary to get a shot at Van Drew in November are Brigid Callahan Harrison, 55, a college professor; Amy Kennedy, 41, a former public school teacher and the wife of former U.S. Rep. Patrick Kennedy; and Will Cunningham, 34, a Black lawyer and former staffer for U.S. Sen. Cory Booker.

The primary has become, in part, a proxy fight between two of the state’s Democratic power centers. The South Jersey Democratic machine, led by power broker George E. Norcross III, is backing Harrison, as is Booker. Murphy, a Norcross foe, and public sector unions such as the New Jersey Education Association endorsed Kennedy.

Kennedy’s campaign has spent about $240,000 on television commercials, about the same as Harrison’s campaign and a pro-Harrison outside group, according to ad tracking firm Advertising Analytics.

The 2nd District includes all of Atlantic, Cape May, Cumberland, and Salem Counties, and parts of Camden, Gloucester, Burlington, and Ocean Counties.

In the 3rd District, based in Burlington and Ocean Counties, Republicans David Richter and Kate Gibbs are running to face Democratic Rep. Andy Kim, who defeated a GOP incumbent in 2018 by less than two percentage points.

Gibbs, 34, a former Burlington County freeholder and deputy director of Engineers Labor-Employer Cooperative 825, was the early favorite.

Richter, 53, a former CEO of construction firm Hill International, started his bid for Congress in the 2nd District but changed course in late January after Trump threw his support behind Van Drew. Richter is campaigning as a “pro-Trump conservative Republican,” and has painted Gibbs as soft on immigration. New Jersey native Bill Stepien, Trump’s deputy campaign manager, has advised Richter’s campaign.

Gibbs has campaigned as a problem solver willing to work across the aisle and says she wants to “bring business and labor together to create jobs, build our infrastructure, and grow our economy.”

A pro-Gibbs outside group has tried to tie Richter to the Biden family, highlighting Hill International’s relationship with Joe Biden’s brother James. “That’s David Richter: buddy with the Bidens, bad for New Jersey,” the narrator says in an ad paid for by the political group Real Jersey.

Also on the ballot Tuesday is Booker, who faces a little-known opponent, Lawrence Hamm, in the Democratic Senate primary. In the GOP Senate race, biotech engineer and lawyer Rikin “Rik” Mehta has won the most endorsements from county party committees, followed by engineer Hirsh Singh. Also seeking the Republican nomination are Patricia Flanagan, Eugene Anagnos, and Natalie Lynn Rivera.

Booker is expected to win reelection easily in the heavily Democratic state.