Marijuana legalization advocates and entrepreneurs fighting to get marijuana legalization passed on election day have a powerful opponent--Sheldon Adelson, billionaire owner of the largest casino company in America.

Adelson, who founded Las Vegas Sands Corporation and owns the Venetian, the Parisian Macao, and other casinos, has donated millions of dollars to four organizations that are fighting ballot measures in Nevada, Arizona, Massachusetts, and Florida, according to financial disclosures.

The Associated Press reports Adelson has donated $2 million to Protect Nevada's Children PAC, which is fighting statewide ballot measure for recreational marijuana Question 2.

(Other casino groups such as MGM Resorts, the South Point casino, and Boyd Gaming have donated tens of thousands of dollars to the same political action committee, the AP found.)

The AP also reported on Monday that Adelson donated $500,000 to Arizonans for Responsible Drug Policy, which opposes recreational measure Proposition 205.

According to the Boston Globe, Adelson donated $1 million to Campaign for a Safe and Healthy Massachusetts to fight Question 4, which is the ballot measure asking if citizens want to legalize recreational use of marijuana.

In Florida, Adelson donated $1 million to fight medical legalization back in September. In 2014, the last time Florida voted to legalize medical marijuana, Adelson donated $5.5 million to fund campaigns against the measure. (It failed by a slim margin.)

Adelson has been a long-time supporter of prohibition and Adelson and his wife own drug rehab center Adelson Clinic, which has locations in Nevada and Israel.

To be sure, the pro-legalization side has its own billionaire backers, from Napster creator Sean Parker to hedge fund manager and investor George Soros. In California, which is home to the largest marijuana industry in the nation but still operates in a gray market with loose medical marijuana laws, the pro-recreational campaign Yes on 64 has raised more than $15 million.

Kevin Sabet, the founder of Smart Approaches to Marijuana, a nonprofit he started with former U.S. Representative Patrick J. Kennedy (RI-D) to fight against full-blown legal markets, says his organization needs help to battle the well-funded organizations and industry entrepreneurs working to legalize marijuana.

"[Adelson's financial support] is a case of someone who's been touched very deeply by drug abuse, and who happens to be a billionaire. We have one. [The pro-legalization movement has] three or four. I still think we're losing in the billionaire department," says Sabet. "What's worse, the pro-legalization billionaires want to make money off of this, whereas the one anti-legalization billionaire is joining others in his industry in saying that stoned workers are bad for workplace safety and productivity."

Sabet says Adelson's donation is "a tiny fraction" of what long-time pro-legalization billionaires like George Soros and Peter Lewis, the late founder of Progressive Insurance, have given to the legalization cause. Since the 1980s, Lewis gave approximately $40 million to drug law reform efforts, according to the National Organization for the Reform of Marijuana Laws (Norml). Lewis told Forbes in 2011 that marijuana laws in the U.S. are "outdated, ineffective, and stupid." Soros is said to have donated $200 million to drug law reform, from medical marijuana to jail-time sentencing reform, since 1994.

In total, five states are voting on recreational marijuana ballots--Arizona, California, Maine, Massachusetts, and Nevada--and four states are voting on medical marijuana ballots--Arkansas, Montana, North Dakota, and Florida--on November 8.

Source: The Inc.