Only a politician on his way out of office can afford to disappoint.

And so it was two weeks ago lame duck President Obama backed away from his promise to take executive action on immigration reform. To be precise, the president characterized it as a postponement of his longstanding promise, one he said he would fulfill later in the year. Translation: right after the November midterms. A more nakedly political decision would be hard to imagine.

On June 30, standing in the Rose Garden, the President had been firm.

He was going to move ahead by the end of summer after the Departments of Homeland Security and Justice weighed in. He declared, “If Congress will not do their job, at least we can do ours.” In June there was a new urgency about immigration reform.

Thousands of unaccompanied children from Central America were crossing the U.S. border. Surely Congress would take action. Instead, Congress rejected the president’s request for $4 million in emergency funding and immigration reform was stalled again.

Now with weeks to go to before the midterm elections, President Obama is falling on the sword for his party. Polls suggest the possibility of Republicans winning seats in the House and Senate. Democratic candidates in too-close-to-call races didn’t want the divisive issue of immigration to be a weapon for their Republican opponents.

But immigrant-rights groups say breaking his promise is a political bait and switch. “It’s like a huge slap in the face,” says Sonia Marquez. Marquez is part of a loud chorus of Latino activists who’ve gone public, charging the president with betrayal and a lack of courage.

“We’ve received nothing but broken promises and a lack of political backbone,” adds Christina Jimenez of United We Dream. Jimenez predicts the president’s delay will mean more than 1,100 undocumented immigrants a day will be deported; action she notes “continues cementing his legacy as the 'Deporter-in-Chief.'”

I think the president’s calculation could backfire. Angry Latino voters may not vote Republican, but they could decide to sit out the midterms, effectively guaranteeing a Republican win in some local and national seats. As one activist put it, “Why are we being thrown under the bus just to keep the Senate, when they can’t prove that it’s going to hurt the Senate?”

Political insiders call the Latino vote 'The Sleeping Giant,' the second most loyal Democratic constituency. The Sleeping Giant elected this president. The Giant has the power to make or break elections large and small.

But more importantly, I know the fiercest political enemies are former supporters who feel their issues are ignored. Witness the growing public criticism of President Obama by African-Americans.

In the coming weeks, Latino political strategists say they will consider how best to flex the muscle of the Sleeping Giant. Be careful not to wake the Sleeping Giant, the warning goes, lest he be filled with a terrible resolve. And that, say Latino immigration activists, is a promise, not a threat.