Democrats have at least one billionaire on their side in US midterm elections

One of the biggest crusades to encourage voter turnout in this year's US midterm elections has been led by the billionaire hedge fund founder Tom Steyer.

The San Francisco-based liberal has pledged $55 million (€43 million) to NextGen Climate, his super political action committee, or PAC, to fund pro-environmental candidates. This makes Steyer the largest Super PAC donor of the 2014 elections, in which overall campaign spending is set to top $1 billion.

This election has seen a record amount of so-called "dark money" being spent by non-profit groups, which are not required to disclose their donors. The 2010 Supreme Court ruling in the Citizens United v Federal Election Commission case allows Super PACs to raise a bottomless war chest to support a candidate as long as they do not coordinate activities with the candidate's campaign.

A recent memo sent by a political strategist to NextGen – leaked to political news website Politico – listed one objective for their campaign: “determine whether there are messages that could degrade Republican voter enthusiasm”. This acknowledges the advantage the GOP has among traditional midterm voters.

Worth an estimated $2.6 billion, Steyer, a Democrat, is seen as the natural arch-nemesis on the ideological dial to the conservative billionaire brothers David and Charles Koch, who are heavily funding Republicans campaigns.

The environmentalist's money has also been spent heavily on negative ads in competitive Senate races in Iowa, Colorado, Michigan and New Hampshire, attacking Republican candidates in those states.

The billionaire is also spending in campaigns to unseat Republican governors in Maine, Pennsylvania and Florida. In the latter, Steyer is one of the biggest donors in one of this election cycle's nastiest gubernatorial races, between former Democratic governor Charlie Crist and Republican incumbent Rick Scott.

Steyer’s message in Florida is that the state needs energy policies that will stop rising sea levels threatening its shoreline.

“The power that we have is the power to vote,” he told residents at Pine Grove Baptist Church on a recent visit to Detroit, where he campaigned to encourage voter turnout in a bid to help embattled Democrats retain their majority in the Senate.