Top Democratic presidential contenders talked tough Wednesday on cutting climate-damaging emissions from oil, gas and coal, turning their focus to global warming in a marathon evening of town halls that gave the candidates a chance to distinguish themselves on a topic of growing importance to their party’s liberal base.

The lengthy climate conversations promised to hand Republicans ammunition for next year’s general election fight by emphasizing one common element in the Democrats’ climate change plans: their overwhelming — and overwhelmingly costly — scope. But the 10 Democrats who participated in the seven-hour series of climate change forums on CNN didn’t shy away from making sweeping promises to reshape the American economy in service of what their party’s grassroots supporters see as the paramount goal of averting global warming’s most devastating effects.

“We have a moral responsibility to act and act boldly. And to do that, yes, it is going to be expensive,” said Vermont Sen. Bernie Sanders, who billed his $16 trillion climate change plan as a necessary response to scientists’ calls for dramatic cuts to carbon emissions.

Former Vice President Joe Biden took a more pragmatic view than Sanders, even as he defended his own climate proposal as “aggressive enough” to meet the challenge. Biden, who has held an early lead in the Democratic primary, has pledged to regulate the oilfield production method known as hydraulic fracturing — though not abolish it, as some rivals have — and said Wednesday that he doubted an outright ban could be feasible. Read more

Read also: Trump denies he suggested Pence stay at his Irish country club

Top Democratic presidential contenders talked tough Wednesday on cutting climate-damaging emissions from oil, gas and coal, turning their focus to global warming in a marathon evening of town halls that gave the candidates a chance to distinguish themselves on a topic of growing importance to their party’s liberal base.