RIGHT SPEAK: 42 Mega-Donors Dominate Super-PAC Donations ... Find Out Who They Are

Forty-two of the nation's superwealthy have donated nearly $200 million to super PACs to shape next week's midterm elections, according to a USA TODAY analysis of contributions of $1 million or more.

In all, this relatively small group has provided nearly a third of the more than $615 million raised by all super PACs in the 2014 election, the analysis of newly filed campaign reports shows.

Liberal environmentalist Tom Steyer dominates the field, having pumped more than $73 million into these amped-up political action committees. Most of his money has flowed to NextGen Climate Action, the super PAC the California billionaire created to make climate change a top priority in several key Senate and gubernatorial races.

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Former New York City mayor Michael Bloomberg, who has made gun control a top cause, is No. 2 at $20 million, nearly 65% of which has gone to the super PAC he created, Independence USA.

Bloomberg, a Republican-turned-independent, has donated to help two veteran Republicans survive primary challenges and has backed some Republicans in state-level contests. But the billionaire's giving has tilted toward Democrats in federal races. He has donated $2.5 million to the main super PAC working to help Democrats retain the Senate majority and another $1 million to Planned Parenthood's political arm.

"This is a handful of people who are really driving this train and driving the dialogue" of the midterm elections, said Sheila Krumholz, executive director of the non-partisan Center for Responsive Politics. "This is a harbinger of things to come" in 2016, when the presidency is at stake.

Super PACs, which can raise and spend unlimited amounts of money as long as they operate independently of the candidates they support, are a potent force in politics. Dozens of them back individual candidates while others — such as Steyer's NextGen group — promote single causes and operate their own ground operations to turn out voters.

In all, super PACs have out-spent the national parties by more than $107 million through midday Tuesday, a tally by the Center for Responsive Politics shows.