WEST DEPTFORD – Three to five million.

It’s the dollar range circulating in the vicinity of Senate President Steve Sweeney (D-3) right now in connection with what insiders say will be a likely New Jersey Education Association (NJEA) campaign challenge to the organization’s legislative nemesis.

Sweeney infuriated NJEA leaders on pensions and benefits, then made a rancorous situation worse last year when he called on law enforcement authorities to investigate the teachers’ union’s alleged strong-arming of legislative members.

Failing the NJEA dredging up a credible primary challenger against an incumbent who has a time-tested Building Trades machine behind him, the labor outfit has a possible and unlikely partner in patrician state Senate Minority Leader Tom Kean, Jr. (R-21).

Four years ago, Kean funded – over the objections of Gov. Chris Christie’s campaign – a Republican challenger to Sweeney.

Sweeney won by double digits, then thumbed his thumbs at the senate Republican caucus leader on Election Night.

Flush with his own dominant election victory, Christie too smacked at Kean with a shrug and an “elections have consequences” quote in Union city when asked about Kean’s legislative leadership lifespan.

But in what would become a first telling sign in Christie’s political downfall, GOP caucus members angry at the governor for making the 2013 general election about himself instead of party-building, defended Kean. In a post-2013 election caucus fight, they reinstalled him as leader over the governor’s stealth efforts to supplant him with Senator Kevin O’Toole, a fierce cross-the-aisle Sweeney ally.

Now Kean, unhindered by a Christie reelection that hinged on protecting Democrats four years ago, has a possible bankrolled shot at Sweeney.

All he needs is a candidate.

All he needs is an NJEA-friendly Republican – a GOP teacher, for example, with a hard-luck story about the Sweeney and Christie years.

“That’s the NJEA’s ultimate play – Kean,” a source today told InsiderNJ.

Whatever ends up happening, Democrats in other battleground districts are concerned.

Will a hemmed in, NJEA-Kean warring Sweeney have to spend millions to stay alive in the already always dicey third, while the likes of Assemblyman Vince Mazzeo (D-2), Vin Gopal, Assemblyman Troy Singleton (D-7) and state Senator Bob Gordon (D-38) are left to fend for themselves in their own state senate campaign foxholes?

Sweeney and his allies are supremely irritated with the NJEA, pointing to the senate president’s fight against vouchers in particular as proof that he and they have common ground on critical issues. But to those old and loyal state Senator Dick Codey of Essex allies, and handfuls of those players close to state Senator Nick Sacco in Hudson, a general election extravaganza might be able to enforce on Sweeney what backroom caucus politics can’t: elimination.

Sweeney says no way.

His kickoff today had Stack-like optics designed to scare off anyone who would cross him in any election – whether a primary or a general. Plus, he proved to Kean once before that the leader shouldn’t try to cross him in Gloucester.

It’s volatile.

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