The biggest news of the governor’s race came and went with relatively little notice: The California Teachers Association endorsed Gavin Newsom for governor.

CTA is the most powerful and sophisticated interest group in state politics. And with their endorsement, Newsom is the all-but-official governor in waiting. For the past 20 years, getting elected governor in California has either required the CTA’s endorsement (Gray Davis, Jerry Brown) or de facto support (which Arnold Schwarzenegger effectively had in 2003, after CTA turned against Davis).

His only significant competitor at this point is former Los Angeles Mayor and Assembly Speaker Antonio Villaraigosa. And CTA will go all out to beat him. Villaraigosa is a former teachers’ union organizer who then battled the union – and has been one of the strongest voices of the state for retaining an accountability system for schools—an accountability system that CTA has successfully dismantled with the collaboration of Gov. Brown and the state board of education.

Villaraigosa would be an underdog even without CTA opposition. He’s Latino in a state with strong anti-Latino prejudices that have reduced support even among Democrats for Latino candidates.

And even worse, he’s an L.A. mayor, which stacks the odds against him to almost zero. How’s that? Well, in the last 110 years the Chicago Cubs have won the World Series twice. Halley’s Comet has swung by the earth twice. And the number of L.A. mayors that have won statewide in the same period? Zero.

Why haven’t I mentioned John Chiang, whom I’ve touted as a potentially strong candidate before in this space? Because CTA’s endorsement of Newsom all but finishes Chiang. The state treasurer’s career has been consistently supported by CTA. His path to victory required either a CTA endorsement or de facto support, and Chiang might well have expected it, particularly in a race against Newsom, who hasn’t always toed the teachers’ union line.

But CTA, like the Godfather, is not sentimental. It’s not personal, just business. It tends to make decisions based on data, and the best read on the endorsement is that CTA’s polling shows Newsom will be next to impossible to beat.

But the endorsement still stings. CTA’s endorsement, in this context, was a betrayal of Chiang. Loyalty is not a two-way street at the union; it expects loyalty, but doesn’t always give it, a point that Villaraigosa should make as much as possible. Look also for Chiang and Villaraigosa supporters to question the ethnic politics of a union whose membership is far less diverse than the schoolchildren its teachers serve. Why did CTA endorse a white candidate early against two other strong Democrats who have a clear commitment to labor and schools?

The endorsement raises fundamental questions about Newsom that he should be pressed to answer. Chief among them: What if anything did he promise CTA to win that endorsement?