Chicago’s second charter strike has now stretched over nine days. Beyond picket lines and hashtags on social media, the Chicago Teachers Union has blocked a lobby of a Loop high rise, delivered labor-themed Valentines to Mayor Rahm Emanuel’s office at City Hall, and even wrangled appearances from the Rev. Jesse Jackson and Illinois Sen. Tammy Duckworth.

How hard will the union push and what’s at stake in its efforts to win a new contract for teachers?

Related: Multiple CEOs, multiple layers: Strike puts charter management under microscope

It could be the future of charter organizing in Chicago, experts say. A victory could “buoy a local wave of new charter school strikes,” said Bob Bruno, director of the Labor Education Program at the University of Illinois at Urbana-Champaign. But if the contract doesn’t bring home the goods, failure could cast a pall over future organizing at dozens of Chicago charters — and untold numbers elsewhere.

Bruno expects in coming days to see increased pressure on members of Chicago International’s board, and possibly even a civil disobedience confrontation that ends in arrests. “They’ll look for ways to demonstrate that the ownership and leaders of this charter operator are not people who are invested in schools,” Bruno said, while “looking for ways to move the employer at the bargaining table.”

But the union’s strategy is risky.

Private employers can permanently replace strikers because its teachers are governed by the National Labor Relations Act, not the Illinois Labor Relations Act which protects public employees.

Chicago International, where teachers at four schools are on strike, has dug in its heels, arguing that granting union demands would bankrupt the network within a few years. “They want a compensation that is fiscally irresponsible for us to agree to,” said LeeAndra Khan, CEO of Civitas Education Partners, one of a handful of management companies contracting to run some of the network’s 14 schools.

The strike also comes in the final weeks of Chicago’s mayoral election. The union has backed Cook County Board President Toni Preckwinkle for mayor, but critics wonder if the union’s effort in maintaining the strike means it’s paying less attention to getting Preckwinkle into office.

But the union has tried-and-true tactics, Bruno said, including political pressure and escalating protests that have helped win tough contract battles in the past. It’s become more combative since the Caucus of Rank and File Educators, or CORE, won leadership of the union in 2010 with a promise to fight against educational inequalities.

That approach helped teachers in the 2012 strike, when thousands of union members went out on a weeklong strike that captured national headlines and pushed their demands beyond just wages and benefits to broader school-quality factors.

Union political pressure also worked in December, when 500 unionized teachers at Acero charter schools in Chicago walked off the job during the nation’s first-ever strike of charter teachers.

Along with pickets throughout the four-day strike at schools across the city, the union also brought attention to how the network had used its political connections to expand. Strikers stormed the office of powerful Alderman Ed Burke, who represents areas thick with Acero schools. Burke then called the network’s CEO and pressed for an agreement. The strike ended shortly afterward.

The Chicago Teachers Union is also known for its staying power in strikes. In 2012, teachers stayed on strike an extra day to make sure that most members were able to review line items of the new contract before it was signed, despite pressure from Emanuel to end the strike. That strike lasted a total of seven days.

In the case of the Chicago International strike, Bruno said the charter network may shoulder the greater risk. The network, which oversees 14 schools run by five charter management organizations, some of which subcontract management to a third operator, has argued that meeting the union’s demands for wages could push the entire network into bankruptcy.

A strong contract that benefits teachers could also push teachers at the network’s 10 non-unionized schools to push for higher wages, Bruno said. “That could be a problem for the employer.”

While the union may be using tactics it has found successful in the past, management of Chicago International doesn’t respond to the same pressures, organizers acknowledged.

If the campaign doesn’t win raises for teachers, or results in cuts to the classroom, Bruno said it could risk slowing down the broader movement to unionize charters. “It gives teachers across the charter school system pause. They are no less interested in having a collective voice but they will remain somewhat uncertain that the union is the appropriate venue for that,” he said.

Richard Berg, an organizer in the Chicago Teacher Union’s charter division, said that because Chicago International and Civitas aren’t political in the same way that Acero is, the union has shifted to focus to the network’s unusual management structure and its connection to big business.

“If you look at their board, it’s not education people or community people. It’s corporate lawyers and money people,” Berg said. “Our strategy has been to say: OK, well, what is going to influence money people to care about children? The morality of it.”

A federal mediator already attends negotiations between Chicago International and the union.  The network requested federal mediation a month and a half ago, and since then a representative from the Federal Mediation and Conciliation Service has been present both at bargaining and in the discussions held independently on each side.

Both teachers and management blame the delay in coming to an agreement on the other side.

“We are determined to make these schools right for our students,” Berg of the union said. “We hope [management] will do the right thing sooner rather than later, because we have thousands of students that are missing school because of management’s intransigence.”

The network, meanwhile, said it’s focused on finding an agreement in negotiations to get back to the classroom. “We are focused on trying to end the strike so that our kids can get back in school,” Khan said.