But the main criticism of New Jersey’s plan centers on setting the benchmark for drawing districts based on statewide election results.
The proposal says that at least 25 percent of legislative districts must be “competitive,” meaning that they must be within five percentage points of the statewide average based on the results for president, senator and governor in the past decade. That formula would likely result in a Democratic statewide advantage of 55 percent, according to a study by the Princeton Gerrymandering Project at Princeton University.
In effect, competitive districts could still have Democratic majorities of as much as 60 percent.
“The map becomes permanently slanted,’’ said Patrick Murray, the director of polling at Monmouth University. He noted that of the state’s 40 legislative districts, at least 25 would have to be majority Democratic under the redistricting proposal.
“It’s the exact opposite of where the reform movements are going right now,” Mr. Murray added. “Not only are they using formulas to give one party an advantage over another, but they’re actually moving away from considering political metrics in their drawing of districts. That includes past vote, voter registration, where incumbents live and a whole host of other things. So this is even a step backward from what the national Democrats are doing.”
The proposal also creates the possibility that Democrats could redraw competitive districts around safe incumbents who have enough support that they would win even with more Republicans added to their district. Party leaders could then add more Democrats to weaker districts.
This scenario has provoked strong criticism from Democratic incumbents who tend to win by large margins in Democratic strongholds like Hudson County in northern New Jersey. “This proposal would create an imbalance of power with representation of North Jersey counties being diluted in the legislature,” Senator Nicholas Sacco of Hudson County said in a statement, “and given that our region is continuing to grow and propel the state’s economy forward that outcome would be fundamentally unfair.”
A growing backlash against the redistricting plan has left the fate of the proposal unclear with just a thin margin of support among Democrats in the Senate.
“If they succeed, and I hope they don’t, I will fight it right through to the ballot box, and you should assume that we ain’t giving up this fight,” Mr. Murphy said. “I’m a proud Democrat, let there be no doubt. I want to win stuff fair and square, and this is not.”