The billionaire climate activist Tom Steyer said on Thursday he would spend up to $100m to attack climate-change deniers in seven key Senate and gubernatorial races.



Steyer's seven picks – Colorado, Florida, Iowa, Michigan, Maine, New Hampshire and Pennsylvania – are among the most competitive contests in this year's mid-terms.

But crucially for Steyer, who will spend $50m of his own money, the races feature Republicans who have denied that climate change is occurring, or who oppose cutting the carbon dioxide emissions that cause climate change.

“The debate on climate change is settled: it is here, it is human-caused and it is already having a devastating impact on our communities,” Steyer said in a statement. “But we need to accelerate the level of political support to address this critical issue before it’s too late.

“This means making politicians feel the heat – in their campaign coffers and at the polls.”

The statement, issued through Steyer's NextGen Climate Super Pac, said the environmental activist wanted to make climate change a wedge issue in the 2014 mid-terms, as well as the 2016 presidential race.

The idea was to demonstrate that anti-science positions could rebound against candidates by alienating younger voters, the statement said.

The campaign said it will also highlight candidates' contributions from oil and coal industries.

Thursday's announcement elevates Steyer's influence on politics from a key opponent of the Keystone XL pipeline project to a national force in Democratic politics.

He spent $11m to help ensure the defeat of a Republican hardliner, Ken Cuccinelli, in the Virginia governor's race last year, and he is the single biggest Democratic donor in this year's elections.

His rising prominence has made Steyer a target for Republicans and has provoked comparisons with the oil billionaire Koch brothers. Steyer rejects such comparisons, saying he does not have a personal financial stake in the causes he supports.

The main targets announced on Thursday include: Republican Senate candidates Cory Gardner in Colorado, Joni Ernst and Mark Jacobs in Iowa, Terri Lynn Land in Michigan and Scott Brown in New Hampshire as well as Governors Rick Scott of Florida, Paul LePage of Maine and Tom Corbett of Pennsylvania.

Steyer is not targetting Senator Marco Rubio, a potential 2016 Republican presidential candidate, who told ABC News this month he refused to accept that the burning of fossil fuels was responsible for climate change.

“I do not believe that human activity is causing these dramatic changes to our climate the way these scientists are portraying it,” Rubio said.

But a number of the candidates on Steyer's hit-list have said similar things.

Scott – though he governs a state already experiencing sea-level rise – has said he does not accept a human cause for climate change. So has Colorado's Gardner, who has said he accepts that the climate is changing, but insists the burning of fossil fuels is not a cause.

Maine's LePage has described climate change as an opportunity.

Brown, a former Massachusetts senator who is running in New Hampshire, does accept the science of climate change. But he has been a strong supporter of the Keystone XL pipeline.

The spending on these races appears targeted to break the heavy hold of climate denial on Congress. More than half of Republicans in Congress deny the burning of fossil fuels causes climate change or oppose actions to deal with climate change, according to the Centre for American Progress.

Republican governors and Republican-controlled state legislatures have been mobilising to roll back measures promoting renewable energy.

“Climate change will not be solved by easy answers or quick fixes, but the path forward is simple,” Steyer said. “Our country must have the courage to solve our climate crisis for the sake of the next generation.”