The likelihood that California will legalize cannabis is rising in the final weeks of the Proposition 64 campaign, thanks to strong political donations, limited opposition funding, and few negative October surprises.

According to filings with the Secretary of State's Office, legalization initiative Proposition 64's supporters have raised $19.7 million. The financial report may be the most accurate yet, because it excludes "contributions in earlier election cycles and contributions between allied committees," which otherwise inflate raw sums by millions of dollars. The main Yes on 64 committee has raised about $15 million, while affiliated groups raised the rest. No on 64 groups have raised just $2.5 million.

Experts have long said it could take $20 million to legalize cannabis in California, if the drive did not face major opposition. By that metric, the legalization push now appears to be on target.

That amount raised for California jibes with the cost of legalization in states such as Colorado, Washington, and Oregon. It can cost about a $1 to $2 per vote to pass the measures. It cost about $1.50 in Colorado, insiders there say. Colorado legalization received about 1.38 million votes and approximately $2 million was spent.

California had 17.9 million registered voters, as of May 2016, according to Public Policy Institute of California.

A record 57 percent of Americans now support marijuana legalization, a new Pew Poll stated on October 12. That number has been holding steady for the last few years.

Driving out the vote is another matter. Those that go to the polls most — like white seniors — are the demographic opposite of the most ardent legalization supporters, including youth voters. The Yes on Prop 64 campaign is deploying its cash to target those voters online and in TV ads.

"This is California, and any serious campaign invests most of its resources communicating to voters through paid and online media" stated Jason Kinney for Yes on 64.

Veteran initiative-runner Bill Zimmer, who is working on Prop. 62 to abolish the death penalty said the likelihood of Prop. 64 success is "overwhelming."

"It's overkill [in my humble opinion]," stated Dale Gieringer, who directs California NORML. "I've been predicting this would be a slam dunk ever since Colorado and Washington legalized in 2012, and I don't see any reason to change my opinion."

Opponents may be out of time to depress support for the measure, barring some tectonic political event.

Zimmerman said campaign funding can sway obscure campaigns. "But when the issue is familiar to voters, and those voters have already formed an opinion, the amount of money each side spends is not as dominating a factor," he explained.

Prop. 64 has consistently been polling in the high fifties. But voters still have time to read their voter guides and reject legalization, said Andrew Acosta, director of No on 64, in an email.

"We would never be able to match the money from the marijuana industry, who see this as investment in the biggest market in America," Acosta wrote. "Voters are just now receiving their ballots and they will have a good chance to see that this initiative is much more of a business plan than it is a social justice movement."

However, state data show Prop. 64's money mostly comes from social-interest donors.

Prop. 64 ends pot prohibition for adults 21 or older that are using, gifting and growing personal amounts. It also regulates cannabis commerce. The roughly $10 billion legal industry could generate $1 billion in tax revenue, to be spent on consumer protections as well as mitigating pot and prohibition's impacts on sensitive groups and communities, such as kids and wildlands.

Technologist turned philanthropist Sean Parker pitched in $9 million, as part of spending on a wide range of efforts including $250 million to fight cancer. Parker's spokespeople have said he has no ties or plans to enter the cannabis industry.

The other biggest donor is the Drug Policy Alliance, which over the last few decades has emerged as the leading drug law reform group in America. DPA has championed the total decriminalization of all drug use. This "health-first" approach is rapidly being adopted by the U.S. government, and several medical groups, including the California Medical Association, which endorsed Prop 64.

And Prop. 64 is clinching key endorsements up and down the state, from the likes of major newspapers, to the appearances on Democratic Party mailers, to Republican Rep. Tom McClintock, who said that he supports legalization because it "takes the criminal profit out of the equation."