WASHINGTON - Democratic presidential candidate Bernie Sanders calls climate change the greatest threat to national security. Hillary Rodham Clinton promises to install more than 500 million solar panels across the country.

On the GOP side, Jeb Bush would phase out tax credits for solar power. Marco Rubio wants to cut the gas tax by 80 percent.

There are stark differences between the two parties on energy and environment issues that underscore the high stakes for both sides in the 2016 presidential race.

After President Obama's two terms, many environmental groups and Democrats fear a rollback of policies on climate change and renewable energy under a GOP president. Business groups and Republicans are eager to boost oil and gas production after years of frustration with Obama.

"At the end of the day, there's a clear choice for all," said Tom Pyle of the pro-business American Energy Alliance. "Either continue the Obama administration's anti-energy agenda or chart a new course that promotes affordable and reliable energy for all Americans."

"Everywhere you look, from New York's Wall Street to Iowa's Main Street, voters are ready for real climate action and the clean energy revolution," countered Khalid Pitts of the Sierra Club, "except if you are a Republican running for president."

Sen. Ted Cruz and Donald Trump are among several Republican candidates who reject mainstream climate science. Ben Carson calls himself a "climate science questioner" and says "the temperature of the Earth is always fluctuating."

Bush said at a New Hampshire town hall last month that he thinks the climate is changing and that "humans have some say in it for sure." But, he added, "What I don't want to do is destroy the American economy as the solution."

Rubio asserted at a recent GOP debate that "America is not a planet" and said that when it comes to global warming, he was "not going to destroy our economy the way the left-wing government we are under now wants to do."

Republican candidates all warn that Obama's plan to curb greenhouse gas emission from U.S power plants could cost thousands of jobs and raise electricity costs for businesses and families.

Clinton, Sanders, and fellow Democrat Martin O'Malley support the president's Clean Power Plan, calling it a legacy-worthy effort to slow climate change.

Republican candidates all say they would approve the Keystone XL oil pipeline recently rejected by Obama. Democrats support the president's action.

Democrats back federal subsidies for renewable energy such as wind and solar power. On the GOP side, the candidates range from skeptical to hostile about a policy several describe as Washington "picking winners and losers."

On coal, after running as one of its champions in 2008, Clinton now calls for protecting health benefits for miners and their families and helping retrain them for new jobs.

Republicans all support coal production and enthusiastically back nuclear energy; Clinton offers cautious support for nuclear power. Sanders has called for a moratorium on nuclear-plant license renewals.