DENVER — In Colorado’s simmering war over education reform, the long-anticipated shot across the bow from the state’s largest teachers union has finally dropped.

On Wednesday, the Colorado Education Association filed a lawsuit challenging a controversial law, passed four years ago, that changed state laws around the hiring, firing and tenure of public school teachers.

“Normally, you think of a loophole in a law,” said CEA President Kerrie Dallman. “But this law is a sinkhole that has literally swallowed up close to 100 teachers.”

Senate Bill 191, signed into law by Democratic Gov. Bill Ritter as part of an effort expected to win the state federal Race to the Top grant money, changed the way teachers are evaluated, compensated, awarded tenure — which, under the law, can now also be taken away due to poor student performance — hired and fired.

Republicans all supported it, but Democrats were bitterly divided.

Some of the stricter accountability measures so prized by education reformers have long been viewed as punitive by the teachers union, a group that has long succeeded in exercising an outsized influence on Democratic agendas.

But at a press conference Wednesday afternoon, CEA leaders made a point of emphasizing that the lawsuit only challenges the mutual consent portion of the law.

“I can’t state strongly enough that we are not seeking to put a halt to teacher evaluations,” said CEA Vice President Amie Baca-Oehlert. “We are filing in court because we believe every aspect of SB-191 must have a beneficial impact on our students, our teachers, and our communities.”

Now, five years after the bill’s passage, after Colorado has seen the education reform movement assert itself not just at the Capitol but in school board races in Denver and beyond, CEA is desperate for a win in the courts.

“We tried hard last year to bring the parties together in order to settle this litigation, and we are disappointed that our efforts were not successful,” said Gov. John Hickenlooper in a statement. “We believe the law is constitutional and fair in its current application and we intend to defend it in the courts.”

The part of the law in question, “mutual consent”, stipulates that administrators can approve or deny the transfer of a teacher to their school; until SB 191 took effect, administrators were powerless to prevent teachers from being transferred to their schools.

“This is making it easier for principals to get rid of experienced, qualified teachers,” Dallman said.

But the architect of the reform law believes the cases of the plaintiffs, teachers let go by DPS after not being able to find a teaching job with mutual consent in the one year period allowed under the law before a district is able to let them go, aren’t the norm.

“In the small number of cases where you have a teacher who’s interviewed four or five times and been unable to find a placement, it’s clear that person’s not the right fit,” said Sen. Mike Johnston, D-Denver, a former principal and teacher who sponsored SB 191.

“In most cases, those folks who are on the open market looking for teaching jobs are getting snatched up right away.”

Hickenlooper, a Democrat who faces reelection this fall, agrees with Johnston.

“Great teachers are the foundation of great schools, and we stand committed to ensuring that every child in Colorado has access to the most effective teachers,” he said in a statement.

“The mutual consent provision in Colorado’s teacher effectiveness law is a critical and common sense policy that allows school leaders to make hiring decisions that best serve students.”

Last year, CEA supported Amendment 66, a failed effort to secure another $1 billion in education funding, even though it would have helped fund many of the reforms included in SB 191.

“This lawsuit should outrage every student, every parent, and every taxpayer in this state,” said Senate Minority Leader Bill Cadman, R-Colorado Springs, in a statement.

“The same union that tried to take another billion dollars from Colorado citizens with Amendment 66, is now trying to create a protected class of substandard workers. Instead of promoting the best teachers for our kids, they are trying to protect the worst ones in our schools. This action is shameful. Our kids deserve the best we can offer them.”

While the legal outcome of the suit is months and possibly years away, its filing is a significant political moment, perhaps the point where Colorado’s increasingly fragile progressive coalition fractures further over what appear to be irreconcilable differences when it comes to education policy.

“For a decade or longer, one of the keys to the dominance of the Democratic Party in Colorado has been their superior degree of party unity,” political analyst Eric Sondermann told FOX31 Denver.

“Democrats have managed to paper over a lot of potential fissures while Republicans have seemed almost permanently and bitterly divided between their various factions.  But this lawsuit may indicate an important rupture, both philosophical and political, in that unified front.

“From the recalls to the troubled roll-out of Obamacare and the Colorado exchange to the voter demolition of Amendment 66, this has been a difficult period for Colorado Democrats.  While they hoped that the new year would mean the turning of the page, this lawsuit could point to a deep internal rift and further political trouble.”

Backers of the landmark reform law downplayed the idea of a possible rift among Democrats, pointing to a recent poll by Denver-based Strategies 360 showing that more than 80 percent of voters support prioritizing teacher performance over seniority when determining layoffs.

“Democrats for Education Reform doesn’t agree with the assertion that there is a fracture in the Democratic Party over education reform,” said Jen Walmer, director of Democrats for Education Reform, in a statement to FOX31 Denver on Wednesday.

“Our polling clearly demonstrates that a large majority of Democratic voters – along with the unaffiliateds and Republicans  – support common sense reforms that were put in place by SB 191. The teachers union is simply out of touch and out of line with Colorado voters priority to ensure great school leaders and teachers are in all of our schools.

“We believe the educational needs of Colorado’s children should be our top priority. Any effort to undermine the reforms of 191 place children second to tired, old special interest politics.”