Thousands of Chicago teachers are expected to begin voting Wednesday on whether to go on strike.

And if at least 75 percent of Chicago Teachers Union members approve after a three-day voting period, the group of 27,000 will have positioned themselves to legally walk off the job in several months.

CTU President Karen Lewis has said she’d like to avoid a repeat of the 2012 teachers strike that ground the country’s third-largest school system a halt, forcing parents to scramble for childcare during seven days of missed classes. That year, nearly 90 percent of teachers voted to strike.

Negotiations between the union and Chicago Public Schools have been going on since November 2014.

Lewis has blamed a revolving door of staff at Chicago Public Schools for some of the delay in hammering out a new contract to replace the one that expired in June.

CPS underwent a change of leadership in July after a contract-rigging scandal that resulted, Lewis said, in new people on the other side of the negotiating table from CTU officials at every single negotiation session. The shuffle made progress difficult, she said.

“We don’t want a strike. We want a settled contract but that’s kind of hard to do without a strike authorization at this point,” Lewis said last week.

A CTU spokeswoman did not return phone calls Tuesday.

The strike vote will happen as CPS is hoping the state will plug a $480 million budget hole, money that Gov. Bruce Rauner so far has refused to provide.

CPS spokeswoman Emily Bittner didn’t respond to messages Tuesday, but said last week that a strike isn’t the answer.

“We’re negotiating in good faith with CTU leadership to reach a fair, multi-year agreement that protects teachers, their jobs and our classrooms – and we encourage CTU to join with us in Springfield to fight for equal funding for Chicago children.”

The cash-strapped school district claimed the union’s proposals would cost an additional $1.3 billion. The CTU disputed that sum.

The soonest a work stoppage could begin is 105 days after a last-ditch effort known as “fact-finding” begins.

The fact-finding process involves three people — one CPS representative, one CTU representative and an agreed-upon independent middleman — who over 60 days review proposals and draft a final proposal that gets presented to both sides.

If both parties vote to accept that deal — and they have 15 more days to consider — those terms become the new contract and a strike becomes moot. If either side disagrees and the deal gets scrapped, the teachers union has to wait 30 days and then can begin a strike.

On Nov. 23, union leaders officially requested the fact-finding process to take place.

But CPS contends it’s too soon to give up on current mediation proceedings and recommended that fact-finding begin on Feb. 8, the same day CPS says massive layoffs could take effect.

The union on Monday filed a grievance with the Illinois Educational Labor Relations Board, saying that mediation has gone on long enough and asking the board to compel CPS to begin fact-finding now.

Contributing: Lauren FitzPatrick