A special water referendum in Edison on Tuesday has two big takeaways for New Jersey politics – one on the state’s new vote-by-mail law and the other on public policy.

Nearly 40% of Edison voters who received VBM ballots for the September 10 water referendum returned them so far, an astonishing number for an off-peak election and potentially a harbinger for turnout models in the off-off-year 2019 elections.

That number could still grow. Any VBM ballots postmarked by Tuesday will still be counted if the Board of Elections receives them by close of business on Thursday.

Edison became the first test of VBM reform signed by Gov. Phil Murphy last month after an emergency session of the Legislature to ensure that voters who cast mail-in ballots in 2017 and 2018 automatically receive them in 2019 unless they pro-actively opt-out.

The Middlesex County Clerk sent mail-in ballots for the Edison water referendum to all 2016, 2017 and 2018 VBM voters.

As a data point, the Edison results could look large in upcoming races for the New Jersey State Assembly in what could turn into the Year of the Unlikely Voter.

It’s also clear that voters have an increased focus on issues related to drinking water, perhaps as a result of the Flint, Michigan crisis and recent attention to the emergency in Newark.

More than 10,500 voters participated in the September water referendum – a turnout of about 18%.

A special school referendum in Warren Township last January had a turnout of just 7.9%, although there was no real controversy attached to it and a comparison between Warren and Edison is really apples and oranges.

Still, VBM ballots in the Warren special referendum made up 32% of the total votes cast. That was before VBM reform was approved that extended the mail-in ballot universe beyond the 2016 general election.

Voter turnout appears to have been spiked by enhanced attention to a water-related local issue.

To put that number into some perspective, voter turnout for a September referendum was about 40% of the total turnout in the 2018 general election for the United States Senate and about 50% of turnout in the 2017 race for Governor.

Another perspective: almost as many Edison voters participated in a special water referendum as did in a 2013 special election for the United States Senate: turnout in the referendum was about 89% of the total turnout in the race for Frank Lautenberg’s seat in the U.S. Senate.