The Democratic presidential debate, in which climate change was mentioned during four of the five candidates' opening statements and then discussed at length later in the debate, laid bare the growing and bizarre rift between the parties on this issue.

Among the Democrats, the candidates were competing to portray themselves as the most progressive candidate in tackling global warming. Independent Vermont Senator Bernie Sanders, for example, cited climate change as the number one national security threat facing the U.S., something no viable Republican candidate for president would do unless they were trying to commit political suicide.

Sanders and former Maryland Governor Martin O'Malley each touted their bona fides on climate change, with O'Malley pointing out that he is the only candidate who has pledged to move the U.S. to 100% renewable energy by the year 2050, which would be a herculean — though potentially achievable even with existing technologies — task.

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"I'm the only candidate, I believe, in either party to do this — to move America forward to a 100 percent clean electric grid by 2050," O'Malley said.

"We did not land a man on the moon with an all-of-the-above strategy. It was an intentional engineering challenge, and we solved it as a nation. And our nation must solve this one."

Sanders, for his part, said something we haven't heard at a Republican debate.

"Today, the scientific community is virtually unanimous: climate change is real, it is caused by human activity, and we have a moral responsibility to transform our energy system away from fossil fuel to energy efficiency and sustainable energy and leave this planet a habitable planet for our children and our grandchildren," he said.

Contrast this with the following from Republican candidate Senator Marco Rubio of Florida, who said at the CNN debate on September 17 that he opposes "left-wing" policy proposals to reduce greenhouse gas emissions, saying, "Every proposal they put forward are going to be proposals that will make it harder to do business in America, that will make it harder to create jobs in America."

Clinton, for her part, cited her role in bringing the U.S. and China together to sign a climate agreement in Copenhagen in 2009. That agreement, known as the Copenhagen Accord, was roundly criticized for its tepid commitments to emissions cuts, but this criticism obscures a key fact — it was the first time that China, which is now the world's top emitter of planet-warming greenhouse gases — acknowledged its responsibility to reduce emissions, rather than prioritizing development above all else.

The deal Clinton and President Obama helped broker, as Clinton spoke of last night, was largely the result of a run-in with the Chinese delegation in a cavernous conference center at the 11th hour of the climate talks.

Clinton and Obama walked in on the Chinese as they met with other developing countries to discuss the proposed agreement, which made for some awkward moments, according to numerous press accounts and this reporter's observations outside that negotiating room.

"When we met in Copenhagen in 2009 and, literally, President Obama and I were hunting for the Chinese, going throughout this huge convention center, because we knew we had to get them to agree to something," Clinton said on Tuesday night. "Because there will be no effective efforts against climate change unless China and India join with the rest of the world."

She continued: "They told us they'd left for the airport; we found out they were having a secret meeting. We marched up, we broke in, we said, "We've been looking all over for you. Let's sit down and talk about what we need to do." And we did come up with the first international agreement that China has signed."

In discussing Copenhagen, which was such a tortuous experience that veteran climate negotiators changed the entire approach to a climate treaty in advance of upcoming negotiations in Paris this December, Clinton may have been trying to rebut criticism from Republican candidates that the U.S. should not act on global warming because China is not doing their part.

"America is not a planet," Rubio said at the CNN Republican debate, noting that China is exploiting fossil fuels around the world to fuel their development.

Republican presidential candidate, Senator Marco Rubio, R-Florida, speaks at a campaign event Thursday, October 8, 2015, in Las Vegas. Image: John Locher/Associated Press

"And we are not even the largest carbon producer anymore, China is. And they're drilling a hole and digging anywhere in the world that they can get a hold of," Rubio also said.

China recently announced that it intends to create the world's largest cap and trade emissions system to cut their climate pollution, which is a step ahead of where the U.S. has gone so far.

In addition to the contrasting viewpoints, the Democrats also spent more time discussing climate change than the Republican candidates did at a CNN debate in September. According to media watchdog group Media Matters, Democrats spent a total of 7 minutes devoted to the topic, including answers to a question and spontaneous mentions.

In the Republican CNN debate, by contrast, candidates spent 4 minutes and 22 seconds on the topic, and only in response to a direct question.

Where do the moderate voters go?

The current political landscape on climate change leaves moderate voters, who favor taking action on global warming but also oppose certain left or right wing policy positions, with few if any choices. The Republicans unanimously reject the mainstream findings of climate scientists, which is that manmade emissions of greenhouse gases are driving global average temperatures higher, melting ice sheets and raising sea levels, among many other effects.

Republican front-runner Donald Trump, for example, has explicitly cast aside decades to centuries of scientific research on this issue.

The concept of global warming was created by and for the Chinese in order to make U.S. manufacturing non-competitive. — Donald J. Trump (@realDonaldTrump) November 6, 2012

"Unless somebody can prove something to me, I believe there's weather. I believe there's change," Trump told conservative radio talk show host Hugh Hewitt last month.

Public opinion poll from 2014 showing support for climate policies among Democrats, Republicans and Independents. Image: Yale Project on Climate Communication

"Obama thinks it’s the number one problem of the world today. And I think it’s very low on the list," Trump said in that show. "I believe there’s change, and I believe it goes up and it goes down, and it goes up again. And it changes depending on years and centuries, but I am not a believer, and we have much bigger problems."

Polling indicates that the majority of Democratic voters as well as a significant segment of Republicans are in favor of taking some steps to rein in global warming, and believe in the scientific consensus on the issue. Conservative Republicans, however, have a much more doubtful outlook on climate science and policy, according to polls from Yale University and other groups.

At the moment, only one party is offering up candidates that reflect the broad American majority view on climate change, with the Republicans hewing to the conservative stance.

And that's not about to change anytime soon.

Meanwhile, global warming marches on, with 2015 almost certain to become the planet's hottest year on record.