There is no guarantee California will vote to legalize recreational marijuana in November, but political operative and father of four Daniel Conway has already staked his future on it.

Conway left his job as chief of staff to Sacramento's celebrity mayor, former Phoenix Suns NBA basketball star Kevin Johnson, to help start the marijuana investment company Truth Enterprises.

He is one of hundreds in the most populous U.S. state already pushing ahead with plans to enter a market experts say will be worth $4 billion by 2020.