California approved a major shift against mass incarceration on Tuesday in a vote that could lead to the release of thousands of state prisoners.

Nonviolent felonies like shoplifting and drug possession will be downgraded to misdemeanors under the ballot measure, Proposition 47. As many as 10,000 people could be eligible for early release from state prisons, and it's expected that courts will annually dispense around 40,000 fewer felony convictions.

The state Legislative Analyst's Office estimates that the new measure will save hundreds of millions of dollars on prisons. That money is to be redirected to education, mental health and addiction services -- a novel approach that reformers hope will serve as a model in the larger push against mass incarceration.

The approval of the ballot measure could also help California grapple with massive overcrowding in its state prisons, which are still struggling to release enough inmates to comply with a 2011 U.S. Supreme Court order.

Although California once led the nation in tough-on-crime policies, like the state's infamous three-strikes felony law, Proposition 47 has led in every poll conducted since it was certified in June. The measure's supporters have been an eclectic bunch, from conservatives like Newt Gingrich and business tycoon B. Wayne Hughes Jr. to liberal performers like John Legend and Jay-Z.

The most vocal opponents of Proposition 47 were law enforcement officials who warned that the measure could make it harder to prosecute felony gun theft or possession of date-rape drugs.

At the same time, a few scattered law-and-order voices, like San Francisco District Attorney George Gascón, did come out in favor of the proposition, dismissing those concerns.

Reformers also vastly outspent law enforcement officials and their allies. The main coalition in favor of Proposition 47 raised $7 million as of mid-October, buoyed by contributions from the likes of Hughes, Netflix CEO Reed Hastings and a foundation backed by the financier George Soros.

Californians Against Proposition 47, meanwhile, garnered less than $500,000 in the same time period. The state prison guard union -- often a formidable force in debates over mass incarceration -- sat the ballot measure debate out.