Tom Steyer's bets on private prisons and coal mining could spell trouble in 2020

When Tom Steyer was running a hedge fund in 2000, he wrote a letter telling some wealthy investors their money would soon flow through an offshore company that would shield their gains from U.S. taxes.

It was routine in finance, but could prove toxic in politics.

Now that the San Francisco billionaire has joined the crowd of Democrats running for president, much of what he did to build his personal fortune, including a stint at Goldman Sachs in the 1980s, could turn off voters. His fund's investments in coal mining and private prisons are two of the biggest hazards.

Part of Steyer's challenge is timing. Wall Street's reputation is in tatters in the aftermath of the Great Recession. Many Democrats are upset about growing income inequality. And billionaires - President Donald