If you haven't been paying attention to the mercurial contract talks between the Portland Public Schools and its largest union, time to start.

After twice taking the temperature of its members' willingness to strike, the union has announced a formal vote on a walkout will occur next week. If members approve, the only thing standing between teachers and the first strike in PPS history is the 10-day notice the Portland Association of Teachers is required to give before a walkout.

In a statement this morning, the PPS called the decision "disappointing," but there's no reason to believe the union will act on the vote—at least not right away. In fact, the two sides have a mediation session scheduled tomorrow.

But if progress on teacher workloads, benefits and other sticking points isn't made soon, a strike becomes increasingly likely. (The Oregonian's been all over this story, so check out their coverage if you want to know more about the extended back and forth). That's because each side in the negotiations has a sort-of-nuclear option it can take in the face of an impasse. For the PAT, obviously, that option is to strike. PPS, on the other hand, can choose to impose the terms of its "best final offer" —an arrangement that would remain in force until the two sides reached an agreement.

And that imposition is what the teachers' union is trying to prepare itself for, PAT President Gwen Sullivan said last week.

"You never want them to impose on you," Sullivan said. "Our folks are restless and they feel pretty disrespected."

There's a lot of rhetoric flying around from both sides at this point, and the particulars of their negotiations can get technical. The most-prominent sticking point, though, is teacher workload. The PAT says the district has more than enough money to hire 174 new teachers—a number Sullivan said still wouldn't amount to as much relief as you'd think (it's true the district has been pleasantly surprised by millions in surplus cash recently). The district, in mediation, has offered 88 new positions, and says it's open to more hires being hammered out in the budget process.

But here's the important thing, and the reason why time is increasingly of the essence. If the district imposes its "final offer," then it's likely the union will call a strike. And as days pass with no agreement there are increasing reasons for the district to do just that.

To make new hires in coming months, for instance, administrators will want to know how many teachers to funnel into the system, and how those hires should be made (there is some disagreement about how many rounds of internal hiring should take place before outside candidates are brought in). And when planning the schedule of next school year, PPS needs to know how many days to include (the district's final offer includes three more days, but teachers have resisted that, saying quality of instruction is more important than quantity). Absent an agreement, the school board could vote to impose all or part of its offer in order to make these decisions.

And then you can almost certainly count on chaos.