New Jersey has finally hit the wall.

For years, voices — including this newspaper — have warned cities and states that if they didn’t get a grip on public pensions wildly out of line with what the private-sector pays, they would one day find themselves unable to fund the basic operations that keep a state or city running.

That day came this week in New Jersey when Judge Mary Jacobson ordered Chris Christie to make the $2.9 billion payment to the public pension fund that is owed, instead of the $1.3 billion he proposes. Unless the decision is overturned on appeal, it will blow a huge hole in Christie’s budget.

Now, Gov. Christie’s decision to make a partial payment is a de facto recognition his state’s public-pension system is bankrupt. The day after Judge Jacobson’s decision, Christie delivered a budget address devoted almost entirely to the public-pension crisis.

Christie’s new plan calls for freezing the existing pension plan and replacing it with a trust that combines defined benefits with cash-balance 401k savings plans, reducing the state’s liability.

In return for substantial health-care savings, the unfunded liability would be paid off over 40 years.

Perhaps the most extraordinary development is that the state teachers union, Christie’s bitterest enemy, is willing to negotiate. It’s a recognition by the union that the fund is so mired in debt it could become insolvent — and union retirees would lose everything.

Christie did not create this problem and in 2011 did get some reforms passed. In retrospect, it’s clear he declared victory too early.

The odds are still against him, but here’s hoping he uses his second term to achieve what he said we had in the first: a real fix.