New York will (one presumes) have a new mayor come January 2014. One question for that mayor will be whether he or she chooses the past or the present.

The (future) present: the new mayor likely will face a deficit of $3.7 billion for his or her inaugural budget (fiscal year 2015). That’s a good seven percent of city tax revenues.

The past: unless Mayor Bloomberg and municipal unions do some serious negotiating in the next few months, the new mayor will face more than a dozen expired contracts — and union leaders requesting retroactive settlements.

As NY1’s Courtney Gross reported yesterday:

Some of those unions say it’s time to pay up, and for many that means back pay. ‘The teachers of New York City deserve a raise,’ said United Federation of Teachers President Michael Mulgrew.

At last week’s budget presentation, the mayor made his position on this matter clear. “No administration is going to have money to give for pay in the past,” he said.”

Nor can union leaders offer to pay for back raises via productivity enhancements, as one cannot be more productive on work that’s already been done.

Should the next mayor think differently from Bloomberg, he or she could be looking at a nearly doubled deficit on school workers alone, with payouts for teachers and other school employees alone totaling a cumulative $3.5 billion through 2014 (see page 29).

The next mayoral candidates can make their desired next job easier for the eventual winner by simply saying right now: Bloomberg is right. No retroactive raises. Union leadership should deal with the current mayor.