Donald Trump's State of the Union Address did not feature a musical soundtrack. But, if it had, surely the orchestral accompaniment would have soared when he got to the line: "We are born free, and we will stay safe. Tonight, we renew our resolve that America will never be a socialist country."

Democrats on Thursday laid out a "Green New Deal" that would eliminate U.S. greenhouse gas emissions within a decade, an effort to make climate change a central issue in the 2020 presidential race.