New Jersey's vote-by-mail system is changing under a new law enacted last month that some lawmakers and county officials are warning could spark confusion.

Democratic Gov. Phil Murphy signed the new law in August. It goes into effect in time for this year's closely watched midterm elections.

The new law mandates that voters who signed up for and got mail-in ballots for the 2016 general election will continue to be sent those ballots for all future elections.

That means that voters who wanted to vote absentee in 2016 but expected to vote at a machine this year in person might be surprised when they turn up at the polls and are told they're mail-in voters.

Voters are able to opt out by sending back a letter they should be receiving by the state.

The Murphy administration argues the new law will expand voter participation.

But Essex County Clerk Christopher Durkin says that it’s been a tight deadline letting voters know about the new law, because mail-in ballots have to go out by Sept. 22.

Officials say that anyone who voted by mail in the 2016 election can still vote in person, but will not be able to do it in the voting booth.

“Their names will still appear in the poll books but it'll be stamped ‘Vote by mail voter.’ They'll still be allowed to vote by provisional ballot and that will count two or three days later when it’s verified they did not in fact vote by mail,” Durkin says.

Vote-by-mail voters make up about 10 percent or less of registered voters in Essex County, according to Durkin. But he says that this may increase now due to the new law.

“As you know people are busy. It’s easier for people to vote from the comforts of their home and send in their ballots so I think this will increase participation, which is always good,” he says.

The deadline to register to vote is Oct. 16 for the Nov. 6 Election Day.